traffic noise pollution essay

Noise Pollution: Urban Traffic Noise Essay

Introduction, noise pollution in perspective, the distinction between noise and sound pollution, reference list.

As the world’s nations continue to scale the heights of development, they inevitably have to grapple with the negative side of the advancements realized therein. Among such consequences is the problem of environmental pollution. The battle against environmental pollution has brought together international bodies, governments at the national level, and organizations within countries. However, the trends indicate that the harder the battle is fought, the more serious the issues of concern become.

Environmental pollution is a multifaceted concept that is constituted by a plethora of independent aspects. One of these aspects, which continue to dominate debates across the entire world, is noise pollution. As cities expand to accommodate their ever-increasing activities, so does noise from all sorts of sources increase. This essay examines noise pollution and distinguishes it from sound pollution with a focus on urban traffic noise.

Existing literature is awash with different approaches to the definition of noise and consequently noise pollution. However, of importance is that the approach notwithstanding, noise bears one characteristic that qualifies any sound to be considered as noise. It tends to impair communication between two parties (Schafer, 1994). In other words, noise is any sound that irritates ears and by doing so, hinders ears from capturing projected sound adequately. In light of this insight, noise pollution is thus the existence of sounds that combine to inflict pain on ears continuously, thus causing discomfort to the listener. This assertion means that in a polluted acoustic environment, any two parties wishing to communicate will do so under some level of strain and the chances of the message being distorted are very high.

Noise pollution has been found to have several adverse effects on the health and well-being of man. Its effects range from damaging ears to have a causal effect on some complex health conditions that have been witnessed in some people. To begin with, noise pollution causes reduced working efficiency as noted by Kryter (1970).

When two groups of people are placed in noisy and non-noisy environments and assigned the same tasks, those in a quieter environment will tend to be slightly more productive than those in a noisy environment. This aspect could be attributed to the fact that noise pollution causes distraction and as such, slows down a worker in a noisy environment. The distraction in most cases is undesirable, but the victims cannot help it since they have to divide their attention to a given extent between the noise and the task. The disparity could be up to 12% improved efficiency for those working in a generally quiet environment (Kryter, 1970).

In addition to affecting the efficiency of a worker, noise can also affect the reaction time of an individual to visual stimuli (Kryter, 1970). If noise is persistently availed and the individual is presented with visual stimuli to react to, the noise may cause the individual to lengthen the reaction time, the individual may also react too fast to such stimuli or get used to the noise and not be affected at all (Kryter, 1970).

The three instances of noise affecting the reaction of the individual may not be desirable during certain circumstances. An individual’s ability to react to stimuli should not be interfered with in any way. The danger posed by altering an individual’s reaction time can be appreciated better in circumstances where the stimulus that necessitates the reaction can cause fatal injury to the victim. The victim may end up suffering serious injuries or dying prematurely.

Besides these two, noise also has an effect on the learning of an individual so that it distracts the individual in a way that s/he is not able to learn, as would be the case in a quiet environment. In a study by Kryter (1970), the individuals used a lot of muscular effort, and their breathing was accelerated too in the presence of noise, as compared to quiet environments.

This study clearly shows that noise may have a non-desirable effect on the speed of learning because even if an individual learns, there is a time difference in the individual learning from a quiet environment and the one in a noisy one. Fast learners are considered intelligent, and most education systems tend to favor such individuals. The effect of noise can thus lead to the classification of some individuals as being less intelligent when in actual sense they are victims of a noise-polluted environment.

Kryter (1970) further noted that noise affected the intelligence of an individual so that when an intelligence test score was taken in a noisy environment, it had a detrimental effect on the results. This observation can be attributed to the fact that noise interferes with the ability to concentrate, as would be the case in a quiet surrounding. Studies carried out to find out if the noise had a bearing on the mental and muscular effort exerted while undertaking a task also indicated that there was a negative effect (Kryter, 1970).

There was an increase in speed by up to 4.3% for typists working in relatively quiet environments and what is more surprising is that they consumed less oxygen by up to 19% less than their counterparts working in a noisy environment (Kryter, 1970). Although some indications suggested otherwise, it was notably clear that noise indeed had an effect on the muscular and mental effort exerted to accomplish a task.

These examples are clear testimonies to the effect that noise can have on human beings. Although there are instances of noise showing a positive effect, the magnitude of such effects is negligible, if compared to the cases in its negative effects (OECD, 1991). However, an important point to note is that whether the effects are negative, which is mostly the case, or positive, studies demonstrate beyond any doubt that noise pollution will, in one way or another, affect an individual’s perception of his or her surroundings and that is not desirable.

The preceding parts of the essay extensively dealt with noise pollution, but at this point, there is a need to develop a clear distinction between these two concepts. Sound refers to stimulation caused in ears by the vibration of any surrounding medium. Sound pollution is thus any departure of this sensation from its desirable quality. Based on the manner in which the two terms are used in everyday activities, it is almost impossible to alienate one from the other, yet the two terms mean two distinct things. Therefore, noise is a type of sound whose effect is always undesirable to a listener. In reference to traffic, not all forms of sound produced by traffic can be classified as noise. Only those that in one way or another cause discomfort to individuals’ ears qualify as noise.

This essay is focused on traffic noise in urban settings; therefore, it is important to understand the various forms of sounds that emanate from traffic and what qualifies them as noise pollution from the onset. It should be clear at this point that it is not possible to mention noise without touching on sound because noise is a certain type of sound, but one can easily examine sound without necessarily touching on noise. This distinction should help in the succeeding part of the deliberations of this essay.

In an urban setting, traffic is inevitable for motorists are part of the economy of any setting. Some cities have attempted to tackle the problem of excessive numbers of motor vehicles by touting bicycles as alternatives with considerable success. However, this move is not possible everywhere; therefore, traffic noise will always be a problem to be solved. Among the many forms of sound produced by vehicles, the following can be classified as noise; the honking of horns, the squealing of tires, sirens, raving engines, and banging doors among others. These examples do not exhaust the list, but outline some of the most common sounds that emanate from traffic.

Several reasons underscore why sounds can be classified as noise and thus eventually cause noise pollution. The unexpectedness of a particular form of sound may qualify it as noise due to the annoying effect that this scenario causes the listener (Kryter, 1970). When a driver suddenly steps on the brake pedal to avert an impending accident, the squealing of tires may cause an annoying effect to a listener who may not be watching the scene, and s/he is thus caught off-guard by the sound. The case may be slightly different for a person who watches the scene from beginning to end because for him or she, the squealing of the tires is registered in mind as being necessary under such circumstances. The distinction between sound and noise is thus evident in the perception of the same sound by the two individuals.

The intensity and loudness of a sound qualify it as noise even in circumstances where it is clearly known that it is necessary. A police or ambulance siren may be anticipated at any time, but still, it irritates people due to its intensity and loudness. The loudness is necessary for traffic to clear the way, especially in the case of an ambulance, but this element makes it more undesirable to the listener. The more intense a sound is, the more irritating it is (Rosen et al., 1962). When the sound of an ambulance siren is compounded by the rave of its engine and honking horns, the sounds form a typical scenario of traffic noise in an urban setting, and this is what forms noise pollution from traffic.

In addition to these two, another quality of sound that makes it qualify as noise and thus pollute the acoustic environment is its inappropriateness (Truax, 2001). In an environment where quietness and calm are desired, when there is penetration by sound from a given source, it is immediately considered noise, and thus it serves to pollute that environment. This scenario happens when the peace and quietness that initially prevailed are destabilized by the sudden presence of undesired sound.

A good example of this scenario is in school or library buildings that are proximate to roads. Although the designers incorporate sound absorbing elements to muffle any noise that may interfere with students or readers, sound may still penetrate as noise to cause disturbance and discomfort based on its loudness and intensity. The idea of the inappropriateness of the sound in these settings stems from the fact that these places require total quietness so that when a tire squeal gets to the ear of a learner who is trying to internalize a concept; it tends to draw the learner’s attention to an unnecessary occurrence.

This discussion clearly indicates that noise pollution occurs when a non-desired sound penetrates a given acoustic space but fails to give instances in which it can be said that sound pollution has occurred. At this point, sound pollution shall thus be briefly put into perspective. In reference to traffic noise, it may not be possible to construct the idea of sound pollution clearly, for the way traffic sounds come out is not anyone’s concern. Sound pollution can clearly be examined under conditions where the quality of a sound being produced is of concern to the listener; for instance, in music. In music, a singer, a producer, and a listener are all concerned with the quality of the sound produced. This assertion means that anything that affects the sound so that it does not come out as it should is polluting the sound.

This can best be understood from a mechanical perspective where the sound is viewed as the wave. Therefore, when there is interference with the wavelength or amplitude of a sound wave in any way, it changes from how it is expected to sound to a different form of sound, which may not be desirable by a listener. This scenario underscores how sound pollution takes place. It can be seen that sound and noise pollution are two distinct concepts, but what should be noted even at this point is that the polluted sound becomes noise.

Urban traffic noise may not necessarily cause any form of sound pollution because no one pays attention to the difference between how certain sounds should come out and how they do come out. The quality of sound seems to matter only in music and other instances such as auditions where the quality of an individual’s vocals determines his or her suitability for a particular task. The case is different in normal life situations where the quality of sound does not matter because it seems not to add any value to the acoustic environment. For instance, a tire squeal may not concern anyone at all apart from the fact that it may announce an emergency of some sort.

When a vehicle suddenly stops, it implies that either an accident has occurred or it nearly occurred. The quality of the sound produced by the tire squeal may not concern anyone at all. Traffic noise thus exclusively amounts to noise pollution in any environment including habitually noisy environments. However, ways of reducing the risk posed by noise pollution to human health should be sought because whether in a habitually noisy environment or a quiet one, noise pollution still affects human health. Polluted sound translates to noise, which makes it equally dangerous to human health, and thus it should be avoided.

Kryter, K. (1970). The effects of noise on man. New York, NY: Academic Press. Web.

OECD. (1991). Fighting noise in the nineties . Paris, France: OECD Publications. Web.

Rosen, S., Bergman, M., Plester, D., El-Mofty, A., & Satti, M. (1962). Presbycusis study in a relatively noise free population in the Sudan. The Annals of Otology, Rhinology, and Laryngology, 71, 727-43. Web.

Schafer, R. M. (1994). The Soundscape: Our Sonic Environment and the Tuning of the World. Rochester, VA: Destiny Books. Web.

Truax, B. (2001). Acoustic Communication. Westport, CT: Greenwood Publishing Group. Web.

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• Sustainable Development Definition
• Noise and Sound Pollution
• Reducing Traffic Noise Pollution in Cairo
• Noise Pollution: Effects, Causes, and Potential Solutions
• Ecological Dimensions of Globalization
• Environmental Influences and Psychology
• Urban Home Gardens for Small Native Mammals
• Invasive Plant Species and Birds in Wattle Park
• Environmental Laboratory Establishment
• Chicago (A-D)
• Chicago (N-B)

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• Noise Pollution Essay

Essay on Noise Pollution

Noise pollution is one of the types of pollution we face daily. Like air pollution, water pollution, soil pollution and other types, noise pollution has a major impact on our health. Atmospheric pollution is not the only pollution we go through, but noise pollution can bring destruction to our lives. According to the World Health Organization, noise pollution is a dangerous health issue. The European Environment (EEA) says noise pollution is responsible for 16,600 premature deaths in Europe alone.

A person continuously facing noise pollution can start meeting health issues and can be dangerous in the long term. Several unpleasant noise distractions can bring problems later in life.

Cities have become noisier with car honking, loudspeakers; traffic, etc. leading to noise pollution. Construction of roads, buildings, apartments and other areas are also resulting in increased noise pollution.

What is Noise Pollution?

According to the WHO, noise pollution is a noise above 65db, which can severely affect both humans and animals. A noise beyond 75 dB can be painful and will affect the person severely.

It is impossible to see the danger posed by noise pollution. On land and under the sea, you can't see it, but it still exists. Humans and other organisms can be affected adversely by noise pollution if it is an unwanted or disturbing sound.                     

A decibel is the measurement of sound. Rustling leaves (20-30 decibels) or thunderclaps (120 decibels) to the wail of sirens (120-140 decibels) are all sounds that occur naturally in the natural environment. If a person hears sounds whose decibel level reaches 85 decibels or higher, their ears can be damaged. The sounds of lawnmowers (90 decibels), trains (90 to 115 decibels), and rock concerts (110 to 120 decibels) are just a few familiar sources that exceed this threshold.

The presence of noise pollution has a daily impact on millions of people. Hearing loss caused by noise is the most common health problem caused by noise exposure. Furthermore, loud noise can also lead to health problems such as hypertension, heart disease, sleep disturbances, and stress. All age groups are susceptible to these health problems, especially children. It has been shown that children living near loud airports and busy streets suffer from stress and other problems, such as memory problems, attention difficulties, and difficulties with reading.

Animals are also adversely affected by noise pollution. Caterpillars' hearts beat faster when loud sounds are made, and bluebirds have fewer chicks when loud noises are made. There are many reasons animals utilize sound, including to navigate, locate food, attract mates, and avoid predators. The noise pollution they encounter affects their ability to accomplish these tasks, affecting their survival.

Noisy environments are not only harming animals on land, but it is also getting worse for animals in the ocean. A once tranquil marine environment has become loud and chaotic because of ships, drilling devices, sonar, and seismic surveys. The negative effects of noise pollution are felt particularly by whales and dolphins. For marine mammals, echolocation is essential for communication, navigation, feeding and mate-finding. Excessive noise can interfere with echolocation.

It is the naval sonar devices that produce the loudest underwater noise. The use of sonar works similarly to echolocation in that sound waves are sent down into the ocean and bounce off objects, returning echoes to the ship that can pinpoint the object's location. Whales' ability to use echolocation is interfered with when they hear sonar sounds, which can reach 235 decibels and travel hundreds of miles under the surface. Research has shown that sonar can make whales strand on beaches and alter the feeding behaviour of blue whales (Balaenoptera musculus), which are endangered. Groups representing the environment have called on the U.S. Department of Defense to discontinue or reduce sonar-based military training.

Furthermore, hydrographic surveys can cause loud explosions from inside the ocean. Deep in the water, oil and gas are found using air guns that send sound pulses onto the ocean floor. There is potential for marine animals to be harmed by the sound blasts and to suffer serious damage to their ears. Additionally, the whales may also change their behaviour as a result of this noise. 

In Spain, bioacoustics researcher Michel Andre is studying the effects of noise pollution with the help of hydrophones. He has gathered data from 22 different locations during his project, LIDO (Listening to the Deep Ocean Environment). Using computers, the lab identifies 26 different species of whales and dolphins, including sounds produced by humans. In the analysis, underwater noise will be investigated for its effect on these animals.

What causes Noise Pollution?

Although the world is turning into the use of technology, at the same time, this technology is also harmful. Industries using compressors, exhaust fans, and generators are producing a lot of noise.

Similarly, bikes and cars with old silencers produce heavy noise that can lead to pollution. Planes, heavy trucks and buses are also part of this noise pollution. Low flying aircraft, especially military ones, causes noise pollution. Similarly, submarines can cause ocean sound pollution.

How Noise Pollution affects a Person?

Noise pollution can primarily start affecting the hearing ability of the person, causing permanent hearing impairment. Furthermore, it can cause an increase in blood pressure, hypertension, and other stress-related health issues. In many cases, noise pollution can cause a disturbance in a person's state of mind, which further causes disturbance in sleep patterns, stress, aggressiveness, and other issues. The psychological health of the person can also get disturbed due to regular exposure to noise pollution.  Noise above 45 dB can disrupt the pattern of your sleep. According to the WHO, the noise level should not be more than 30db. Change in the sleep pattern can also bring change in your behaviour.

If you have pets in your home or around your area, then noise pollution can bring a negative impact on the environment. Firecrackers can bring fear in them if they are regularly exposed to them. This will also bring change in their behaviour.

Effect on Wildlife and Marine Life

Animals and marine life are vulnerable to noise pollution. It can affect their listening skills, which further affects their behaviour pattern. These animals find it hard to listen during migration, which can negatively affect their lives. When it comes to marine life, noise pollution can lead to internal damage like physical problems in them.

Measures for Noise Pollution

There are many measures taken by the government and people to reduce the effect of noise pollution. Soundproof walls and windows are now being installed in many houses. Many flyovers in cities have soundproof walls to bring down the noise level to a nearby resident from vehicles running. As responsible citizens, we must contribute towards bringing down noise pollution. Needless honking should be stopped and officials should fine people doing it heavily. Hospitals and schools are built-in silent zones.

There should be rules to avoid noise in residential and sensitive areas. People need to be aware of health hazards from noise pollution.

One of the best ways to bring down noise pollution is by planting more and more plants. This process of planting trees can help to reduce the travelling of noise from one place to another.

Noise pollution is the most common problem faced by humans, thanks to various reasons that push many people to face health issues. Following standard measures can be helpful in the long term for both humans and the environment. The ultimate aim is to bring down noise pollution for a better environment.

Noise Pollution: Impact on Human Health

There are several ways in which noise pollution can harm human health:

Having an elevated blood pressure for a long period directly results in hypertension, which is caused by noise pollution.

Hearing loss occurs whenever humans are repeatedly exposed to sounds that exceed what their eardrums can handle, resulting in permanent damage to their hearing.

To function properly at work, it is necessary to get enough sleep every night. Sleep disorders affect energy levels throughout the day. Pollution causes disturbance in sleep cycles, which in turn results in irritation and unrest.

Heart issues such as blood pressure level, stress and cardiovascular diseases can arise in a healthy individual, but a person suffering from heart disease may experience a sudden increase.

It will affect your mental health also very badly because continuously hearing the noise this much loud will pressure your eardrums and that will badly affect your brain also

FAQs on Noise Pollution Essay

1. What are the significant factors causing noise pollution?

Multiple factors can result in noise pollution. Some of these are massive honking during road traffic, construction, poor urban planning, loudspeaker and others. Furthermore, firecrackers, the noise of bands and others can also result in noise pollution.

To eliminate or decrease noise pollution, it is crucial to know their effect. This will help to create measures and work towards it.

2. How can noise pollution be controlled?

There are different ways of controlling noise pollution. Some of the measures are-

Control at Receiver's End - For those people who are working in noisy installations- they can work on ear-protection aids like earplugs, earmuffs, noise helmets, etc.

Reducing Noise from Vibrating Machine - Another way is by the noise produced from the vibrating machine by vibration damping, beneath the engine.

Planting of Trees - One of the best ways to reduce noise pollution is to plant more and more trees along roads, around hospitals and schools.

3. Who is at the risk of the health effects of noise pollution?

When it comes to the effect of noise pollution, the risk of health effects can be for any age of the person. Sound louder than 80 dB can be hazardous. Be it, kids or young adults, high decibel sound can affect ears. People who listen to headphones can face noise-induced hearing loss issues. Additionally, there is the current scenario where people are completely used to using headphones and gadgets that impact their hearing ability. Because of that, those people are more likely to experience health problems caused by noise pollution.

4. In what different ways can noise pollution cause health problems?

We can say that there are three types of pollutants:

noise from transportation

transportation

transportation, noise from the surroundings

surroundings

surroundings, and industrial noise

Noise from transportation: Traffic noise is mainly responsible for this disturbing noise, which has increased greatly since the number of vehicles has increased. Increased noise pollution causes older people to lose their hearing, headaches, and hypertension, among other diseases.

Noise from the Neighbourhood: Electronics, household utensils, etc. cause a lot of noise. Musical instruments, transistors, speakers, and others are the most common sources.

Noise from Industrial Processes: An industrial machine produces an especially loud noise due to its high intensity. A large number of studies have shown that industrial noise pollution damages hearing by 20% to 30%.

5. How does noise cause environmental pollution? What are the reasons why noise pollution must be taken seriously?

Noise pollution is caused by extreme noises generated by sources such as industry, transport, loudspeakers, etc, which adversely affect human health by causing headaches, migraines, mental imbalance, nervous breakdowns, and heart diseases.

There are numerous health hazards associated with noise. The following are some of the physical, physiological, and psychological effects of prolonged exposure to noise:

A reduction in sleep is one of the effects of repeated exposure to noise.

Noise noise, which affects human productivity and efficiency.

Taking pictures of someone invades their privacy and disturbs their peace of mind.

• Essay Editor

The Effects of Noise Pollution

1. introduction.

The term noise may, to many people, suggest only sound that is loud. However, in its more general sense, the term encompasses all unwanted sounds which can be found in our environment which is commonly referred to as noise pollution. This is a global issue which is growing by the day, and adversely affects human health and well-being. Noise pollution has now been recognised as a major source of danger to physical and mental health. Noise is defined as 'excessive or displeasing sound'. This article aims to explore the health effects of noise, with particular regard to the mental health of individuals. There are many sources of noise pollution, including noise produced by transport systems, road traffic, rail and air, industrial noise, and noise produced within the building from various types of machinery. Indeed, Davies and Price represent noise pollution within the UK to have risen to an astonishing level with 40 million people being exposed to road traffic noise, 4.7 million people exposed to aircraft noise, and 3.9 million people being exposed to noise from industry. This means that people are finding it increasingly difficult to escape the intrusion of noise into their lives. A recent UK study suggests that single exposure to a very loud noise such as an explosion, has reduced from 49% in the 1980's to 35% in the 1990's. However, during the same time period, exposure to noise from road traffic has increased from 34% to 64%. There are numerous health effects of noise which vary depending on the individual and duration of exposure. These can be broadly defined as physiological or psychological impairments. The psychological effects of noise can be the most damaging as they can change an individual's behaviour and personality. This can in turn affect a person's relationships with others and vulnerability to social and environmental pressures. It is here, where noise-induced mental disorders are said to appear, noise has been linked to anxiety, stress, nervousness, headaches, irritability, anger, emotional instability, depression, disorganization of thought and general mental distress.

1.1 Definition of Noise Pollution

Definition of noise pollution is any noise that is unwanted, disruptive, or hazardous to the activity or balance of life. The word noise is derived from the Latin word nausea meaning disgust. Noise is not only an unwanted sound but also a source of great irritation and discomfort to the human beings. The term noise may be confused with sound. Acoustically, sound is very much essential to our life. It is a form of energy that helps us to hear. On the contrary, noise is a sound that is undesired by the recipient. A sound may become noise pollution if it disturbs the normal activities such as sleeping, conversation, or disrupts or diminishes one’s quality of life. Any sounds that disturb the normal rhythm of life are classified as noise. A normal healthy person can suffer physiological damage in the presence of noise levels above 110 dB. Any sound that is loud enough to cause discomfort in normal activities can be considered as too loud. Noises are usually considered to be a man-made phenomena. Indeed, man is a slave of the industrial civilization. He will go to the boon docks in search for a better quality of life, with modern day transportation and machines trailing. The movement of machines and transportation with their characteristic noise, have built up to crescendo in the recent decades. This industrial, mechanical noise is very pervasive and since it is a source of irritation, it can be classified as noise pollution. Modern day civilization is surrounded with myriad of conveniences and technological marvels. They have indeed made our life more comfortable but the hazards to the environment and health have made them a double-edged sword. Household machines are indispensable in the running of a smooth household, but a house built near a busy street can suffer noise pollution from the racing traffic, that will render the indoor environment of said house too loud for conversation or peace. Steps to eradicate or reduce noise must be taken. Cognitive dissidence, such as discussion the necessity of owning a car and the consequence of contributing to noise pollution, is a start to eventually begin the cures for noise pollution.

1.2 Sources of Noise Pollution

Road traffic noise is the main problem and is increasing day by day in every city. The main cause of this is the ever-growing number of vehicles throughout the world. Aircraft, railroads, construction equipment, manufacturing processes, home gadgets, and various appliances are the chief sources of noise. In rural areas, trains and airplanes contribute to the pollution. Multifamily dwellings, attached houses, and condominiums contribute to noise pollution through architectural design that often results in massive sound transfer between units. In recent years, methods of disrupting human comfort at home have increased. Power tools, lawn mowers, and leaf blowers have very adverse effects on the quality of urban life. These effects of noise on human well-being are a health hazard. Changes in the structure of communities near industrial areas, starting of factories and shift work have led to increased complaints about sleep disturbance from noise. High-intensity sound causes temporary or permanent loss of hearing. High aircraft noise in areas on the flight path near the airport can cause emotional stress, which may have a detrimental effect on the people in the community. High frequency, loud, sudden, and impact noises are usually the most harmful. They can cause annoyance, anger, and sometimes aggression. Behavioral effects of noise can hinder work efficiency and effectiveness. This can be very damaging in situations where much is at stake. In today's highly competitive society, the last thing someone needs is a handicap to the ability to perform to the best of his or her capabilities. It has been difficult to prove the effects of noise exposure on the sick, on the elderly, and on children, let alone that of noise-induced psychological dysfunctions. However, it can be said that the general effect of noise on these groups is usually more severe because they are lacking the efficiency and strength of the healthier adult population. This being the case, it makes the disablement to the less capable an even bigger problem.

1.3 Impact on Human Health

The relationship between high noise levels and human health is widely recognised. Noise has been known to have a number of profound behavioural and physiological effects which are influential in daily life. Exposure to noise at home, school and work has been associated with a number of health problems. It can affect our mental health and well-being and cause long-term illness. The 'distress' caused by noise can be a cause of acute or chronic health problems. A feeling of helplessness and the belief that the source of the noise cannot be controlled can generate stress. Often it is not the source of noise, but an individual's perception of the sound, that determines whether it becomes a health problem. Noise can also affect air. The non-auditory effects of noise are those that do not affect the mechanics of the ear but can affect an individual's quality of life. Cognitive effects are defined as changes in behaviour or functions in the brain. High noise exposure has been known to impair performance on complex tasks and to decrease motivation. This can be explained in terms of the Information Theory. The model suggests that all information is taken in by the five senses and any interference with the 'message' results in an increase in entropy or information loss. The result is that more information needs to be taken in to understand the message and mental task performance is less efficient. Sleep is a necessary and vital physiological process that provides rest and recuperation for both mind and body. An individual's quality of sleep can be impaired by noise and cause changes in mood, work performance and general well-being.

2. Environmental Consequences

It is a modern creed that "The environment belongs to the whole society" and for man to manipulate with is at the risk of his own self. Environment is getting worse and worse day by day because of the industrial revolution and increasing of technology. Increasing in industries has led to an increase in air pollution, water pollution, and land pollution. But one more pollution has been added to this, which is a special agent of the change in the natural environment itself, and nowadays it becomes a major cause of environmental degradation. Noise is defined as unwanted sound. It is an environmental stressor and is a form of air pollution. It is any sound that is undesired and causes disturbance. Miracle of modern science, noise is an adverse sound, which in some way would impair hearing or physiological functioning. Traffic is the biggest culprit of noise pollution, other sources are aircraft, rail, transport, industry, and construction. Mainly three are four sources which cause noise pollution in our environment, they are the transport sector, industry sector, buildings, and the public address systems. With the development in the field of science and technology, the cable cars and the sky buses moving on the aluminium or other types of rails are causing heavy noise pollution in the hilly areas. While the noise from the airplanes and the military jets flying at sonic speeds can have repercussions on the human and animal life. But the most dangerous and the most harmful source of noise pollution is the noise of heavy machineries and the generators used in the factories. High-intensity noise causes temporary or permanent nervous system damage by changing the blood pressure, hormonal release. It also affects the digestive system and the annoyance adversely affects performance of mental tasks.

2.1 Disruption of Ecosystems

Exposure to noise pollution has been shown to have a profound impact on a variety of different ecosystems ranging from terrestrial to aquatic and even subterranean. The adverse effects that noise pollution can have on an ecosystem are not always obvious. While often times disruptive effects are seen from the subsequent responses to changes in species presence, abundance or diversity. A common response to noise pollution is the masking of environmental cues that are of importance to certain species. Animals depend on environmental cues, often acoustic, to aid in the detection of predation, selection of mates, location of prey, and ultimately the avoidance of unfavorable habitats. If these cues are masked by noise, animals may be forced to make a decision to abandon the area or expend more time and energy in the completion of those tasks. Success rates of these critical behaviors are important to the overall fitness of the individual and the viability of the population. A decrease in success rates and the subsequent changes of animal behavior can lead to changes in species' abundance and eventually affect the diversity of an area. In recent years there have been growing concerns over the effects of noise pollution on marine mammals. Oceanic surveys have shown that noise levels in the oceans have doubled each decade for the past 60 years. This is in part due to the increase in shipping, seismic surveys and naval sonar. The increase in noise has led to concern over its potential effects on marine mammals and has been the driving force for a significant amount of research in this area. The most extreme cases of impact have been the mass strandings involving the death of several different species of cetacean. While it is extremely difficult to pinpoint a cause for these strandings, post-mortem examinations of stranded animals have revealed a variety of lesions and abnormalities which are consistent with gas bubble disease (also known as decompression sickness). This disease is caused by a sudden decrease in pressure and the formation of gas bubbles in the body. It is believed that changes in ambient noise levels may scatter animals and cause them to dive and surface more frequently, thus changing the pressure at which they perform physiological functions. The most commonly reported behavioral effects involve the displacement of animals from areas of high to low noise levels and changes in the timing of activities. Due to the complexity and subtlety of many of these responses, effects of noise pollution can often go unnoticed and may take a long time to reverse. In extreme cases though, the disruption of an ecosystem from noise pollution can cause a cascade of effects that lead to a total collapse and conversion to a different system. An example of an extreme case would be the desertion of an area by an acoustic specialist species. Studies have shown that several species of bird avoid areas with high noise levels coming from natural gas compressors. It was observed that the absence of these birds caused a significant increase in arthropod abundance and a decrease in the overall vegetation cover. This chain of events resulted in a change to the entire food chain of the area.

2.2 Effects on Wildlife

The animals need to hear what is going on in their immediate environment. When animals are exposed to frequent noise, the physiological effects are very similar to those seen in humans. This can cause them to become more stressed. In a recent study, anthropogenic noise was simulated to investigate the effects on stress hormones in mule deer. The study's intention was to discover the implications of increased development and human recreation in mule deer habitat for a 50-year period. The noise-polluted environments caused short-term physiological stress in this species by increasing cortisol and catecholamine, and the presence of hunters created a more pronounced stress response. Typically, white-tailed deer are a keystone herbivore in forests and they serve as a prey species for large predators. Deer can easily become startled, so they often "jump the gun" with their fleeing from perceived danger. This behavior is often an anti-predator defense. A chronic exposure to noise can cause deer to alter their spatial habitat use, timing, and fleeing responses, thus altering the community structure of their predators and other herbivores. Runners et al. said, "Habitat use represents the spatial and temporal distribution of animals in their environment, and suitable habitat is that which allows an organism to maximize fitness through its life history requirements" (2006). If the deer are avoiding suitable habitat because it is too close to potential noise sources (such as construction and logging), this may put them in further danger due to poor habitat selection. Noise pollution can be particularly detrimental to certain species of birds, which rely on their auditory senses more than others. This includes those that have evolved to forage in the substrate (insects, leaf litter) and those that are already under threat due to habitat destruction. Both of these effects can be seen in ovenbirds and American woodcock.

2.3 Noise Pollution and Climate Change

Emissions of greenhouse gases are one of the major sources of pollution caused due to human activity that leads to climate change. However, the effect of noise pollution on the emission of gases has not been widely studied. Research has shown that noise pollution can have a large impact on the production of greenhouse gases into the atmosphere. Noise pollution has been seen to increase physiological stress on animals, which can cause an increase in their breathing rates. Respiratory metabolism can be altered in birds due to noise pollution, and an increase in their energetics can mean an increase in carbon dioxide production. Noise pollution can cause a change in species behavior, which can lead to an increase in energy expenditure and result in a greater output of carbon dioxide. The alterations to ecosystems caused by noise pollution can lead to changes in the decomposition process. This has been seen in a study in US national parks where an increase in background noise has led to a reduction in the rate of leaf litter decomposition. This is significant to the production of carbon dioxide as it is produced during the process of decomposition. It is difficult to quantify the effect of noise pollution on climate change due to the vast amount of factors that are involved. More research is needed to form a clear link between noise pollution and climate change, but it has been shown that there is potential for noise pollution to be an amplifier to climate change.

3. Social and Economic Impacts

Increased urbanization and industrialization have resulted in an increase in the levels of noise that disturb the environment. Unwanted sound (noise) can damage psychological and physiological health. Noise pollution can cause annoyance and aggression, hypertension, high stress levels, tinnitus, hearing loss, and other harmful effects. Furthermore, stress and hypertension are the leading causes of health problems. Evidence from the past 50 years has shown that there is a direct link between high levels of noise and hypertension. A study on healthy individuals exposed to recorded traffic noise, aircraft noise, and the sound of a thunderstorm showed that the systolic and diastolic blood pressure increased compared to the periods of no noise exposure. In the long term, high blood pressure is a main cause of stroke and heart disease. It has been noted by Cohen et al. (1980) that the most significant effects of noise, apart from mild hearing loss, were emotional or psychological in nature and not disorders of the auditory system. People exposed to noise from various sources are aware of the adverse effects of this noise on their work performance. Experimental studies in laboratory settings or field studies of noise on school children and students have shown that noise affects the cognitive and attainment ability of such individuals. Usually, the effects are obtained from comparisons of ability test results with varying levels of noise intensity. This has been simulated in studies of aircraft and road traffic noise on people living in the vicinity of airports and near busy roadways. The findings unanimously showed that the test groups exposed to noise performed less effectively than the control groups not exposed to the same noise. In many of the studies, the exposed test groups also showed more errors of omission and commission, which is an indication of decreased task efficiency. He noted that cognitive responses to noise usually involve a person's conscious assessment or evaluation of the noise and is a precursor to future behavior. Any noise that is judged to be unfavorable will invoke attempts to control the noise or escape the situation. Various behavioral changes can in turn affect the productivity of an individual in an occupational setting. It is well known that productivity is synonymous with performance and that changes in productivity, good or bad, have an impact on the economic status of an individual or a nation. High noise exposure has been shown to cause a decrement in performance varying from temporary to permanent. This decrement can affect the economic status of an individual, business, or nation and has various opportunity costs. Any effects on the general population or specific groups within it, which change normal social and economic behavior, will have a collective impact on the nation's economy. The sum of individual impacts can affect the social fabric of a community by reducing opportunities for human capital accrual. This in turn can influence a community's future economic prospects. Noise even has the potential to act as a barrier excluding certain groups from an activity. Noise has various direct and indirect costs to performance and has been traditionally assessed by the use of specific performance tests, general task efficiency, and the amount of time to complete a task.

3.1 Noise Pollution and Quality of Life

The subjective nature of noise and its impact upon an individual's quality of life can be very profound. People who are exposed to higher levels of traffic noise have reported to have higher levels of stress and are more likely to have stress-related illnesses. Studies have shown that there is a direct link between noise and aggressive behaviour. This has been seen most readily in individuals who live near airports and have to endure the sounds of airplanes flying over their house. This has prompted studies to determine whether or not chronic exposure to noise acts as a catalyst to high blood pressure. Effects on social behaviour and the general well-being have also been reviewed. Unfavorable changes in social behaviour have been linked to children in noise-exposed schools. A Dutch study compared students from noisy schools to those from quiet schools. They found that the students from the noisy schools were more likely to show signs of annoyance and anger. A similar study in London compared the behaviour of children in different areas. It was concluded that children who lived in areas exposed to high noise levels were more likely to be involved in antisocial behaviour. In Germany, it was noted that the majority of complaints in communities and households affected by noise were to do with the general disturbances to what they considered to be a normal lifestyle.

3.2 Effects on Productivity and Performance

The effect of noise pollution on productivity and performance is an important one due to the fact that as individuals we are surrounded by sound. Sound is what we hear and can be pleasant, but at the same time sound is what we are subjected to that is unwanted and annoying. Unwanted noise can have a negative effect on the task an individual is doing and may cause a decrease in efficiency and effectiveness, and hearing loss in the long run. One of the key areas where individuals are affected by noise is in the workplace with the fact that in many occupations, performance and productivity are the most valuable asset to an employer. Hearing loss induced by noise is the most common and also the most preventable occupational injury in the world. Industrialization has brought economic growth and technological advancements. This has however been at the expense of an increasingly noisy world. The Health and Safety Executive estimate that over a million people in the UK are exposed to noise levels which put their hearing at risk and there are many more affected by loud noise in the services sector at work. High noise levels can cause stress, ulcers, high blood pressure, and migraines and headaches. These can in turn affect the quality of work and the worker's morale. Stress can lead to a decrease in the immune system function and an increased susceptibility to disease which will also affect work performance. A factory survey in the USA found that the yearly rate of absenteeism due to noise exposure for 100 workers was 4.38 compared to 2.89 for 100 workers not exposed to high noise. High absenteeism levels are obviously detrimental to productivity and work performance. High noise levels can also mask auditory warning signals and make communication between workers difficult. This could lead to an increase in accidents, another factor which impairs work performance and productivity. A Dutch study estimated that in industries where noise levels exceeded 80 dBA, 21% of accidents were due to noise being a causal factor. High noise levels in the working environment can also bring about irritability and aggressiveness from workers. This will reduce group cohesiveness and undermines the effort to create better safety behaviors at work. The net result of this is a decrease in work performance and productivity.

3.3 Economic Costs of Noise Pollution

Economic factors are perhaps of most concern in our society because they can affect everyone from the individual up to the national level. In the UK, it was estimated that the social cost of environmental noise in 2000 was between £7-10 billion pounds, equating to between 0.7-1.0% of GDP, with the majority of this cost being incurred on the individual, approximately £6 billion pounds. Just under half of this can be attributed to sleep disturbance and its consequences. The other half is mainly an estimate of the monetary value people place on their well-being if it was reduced by noise and annoyance. The cost on the individual primarily affects those living in urban areas, and it is not always the case that those most exposed to noise are most affected. Shift workers and the elderly are particularly vulnerable. On the link between noise and sleep disturbance, quality of life, and well-being, states "Recent studies conducted in Europe estimated that sleep disturbance from aircraft noise has a value of around 7500 Euros per person per year. This was largely attributed to lower performance at work and increased use of healthcare. The cost consists of attempts to reduce noise at night, increased use of sleeping pills, and the value of health and cognitive functioning that is lost as a result of sleep being disturbed." This study also showed that those with more noise-sensitive personality traits will incur greater costs to prevent further increases in noise. Causes of sleep disturbance by noise and the efforts to reduce its effects can be identified as a problem area where expenditure and cost-effectiveness is particularly relative to incidence and is an area that, when noise is reduced, can show major benefits.

4. Noise Control and Mitigation

Noise pollution can be controlled and mitigated by several methods. One of the most important methods of control and mitigation is implementing noise regulations at governmental levels. These regulations are based on setting standards of noise limitation or acceptable levels. By doing so, it is possible to stipulate the acceptable levels of noise in various zones of land use, to restrict the overall level of noise in given areas. Penalties can also be set for those who exceed the noise limitation, and thereby provide deterrence for those who violate the regulations. Another method of controlling noise is to define noise emission standards for various sources such as vehicles and machinery. This sets the maximum allowable noise that can be emitted by such sources and effectively limits the resultant environmental noise. Noise regulations and standards are effective in controlling and reducing noise at the source, however the success of such methods relies on the extent of enforcement and the willingness of the sources to observe the regulations. The growth of knowledge and public awareness of the effects of noise pollution has led to the implementation of various forms of controls and mitigations through public involvement and education. This can take the form of local community groups or organizations that seek to address noise problems in the local area. An example is the establishment of "quiet communities" in the United States, where specific cities and towns aim to reduce the overall noise impact on its inhabitants. Community involvement may also be directed at seeking to influence public policy on matters that can affect the noise climate. This can range from anything to voicing concerns over a new highway construction to national interest groups lobbying for stricter controls on noise emissions from specific sources.

4.1 Noise Regulations and Standards

Wherever it occurs, noise can have a harmful effect on health. It is accordingly right that noise is considered as a pollutant, and it is right and proper that loud noise is subject to control. Noise regulations are essentially aimed at places where people live, at times when they rest and sleep, and at protectors of our society such as hospitals and schools. Consequently, regulation can be directed at specific points or it can have a wider purpose. In other words, it can be site-insensitive or site-sensitive. Noise regulations and standards play a vital part in influencing people to control and mitigate noise. They are an essential facet of noise policy in industry, transportation, construction and town planning, and in the formulation of laws for the control of noisy domestic appliances. Noise regulations concern the acoustic environment and its effect on comfort and well-being, but they are made with regard to economic and social costs and benefits. Thus the assessment of noise and its effects can involve economic and social analysis. Regulations and standards can range from the setting of maximum limits for specific noise indicators or maximum allowable increases over existing ambient noise levels, to more qualitative measures aimed at preserving acoustical environments suitable for various activities and communities. The regulated community (particular social group or geographical area affected by noise) will always be seeking effective protection from noise, and those responsible for noise sources will always be seeking acceptable and cost-effective means of compliance. This interaction of supply and demand is what makes regulation effective, and what drives technological development in noise control and its integration into the design of products and environments.

4.2 Strategies for Noise Reduction

Effective noise control begins with an awareness of the specific sources of noise and the circumstances under which they occur. Once the key locations and activities generating excessive noise have been identified, strategies can be formed to reduce noise levels. There are many ways to control and reduce noise; the most successful and cost-effective strategies are those that address the root of the problem. At present, a graded approach to environmental noise management contends that each and every one of us should accept responsibility for the noise that we generate, and the effect that it has on other people. This approach to noise management is an important step to reducing the noise that affects our health and well-being. Specific strategies of noise control fall into four general categories common to all environmental management: Legislation and Planning, Establishing Better Practices, Noise Reduction by Design, and Soundproofing. Legislation and planning ordinances are the first step in avoiding and controlling noise. In the UK, excess noise has since become recognized as a statutory nuisance. This led to the Noise Abatement Act of 1960, and by the mid-1990s, specific noise and nuisance provisions had been incorporated into most environmental legislation and planning control statutes. The identification of certain planning conditions and decision notices were developed to control noise upon the environment. At an international level, the European Commission has implemented policy and indicator values for noise, as well as action plans and strategies to protect residents from noise irritation. These legislations at local and international levels have contributed to greater awareness of the subject and have proven to be an effective tool in noise avoidance and control.

4.3 Community Involvement and Education

The involvement of the community in noise issues and the nascent but potential role of education as a tool for prevention are both areas which have been recently receiving attention. This is in part due to the recognized limitations of legal and technological approaches to the noise problem. The effectiveness of legislation has frequently been blunted by compromises in the form of exemptions and variances, and by the lack of resources for implementation and enforcement. Legal standards in many countries have not been based on public health criteria, with the result that priority areas for preventive action have frequently been neglected. In terms of technology, while great advances have been made in the development of low noise products and processes, these have frequently been offset by increases in the scale and volume of noise sources, so that the overall effect has been adverse. The shortcomings of legal and technological approaches have meant that noise control has rarely been a political priority, and consequently, there has been little sustained commitment of resources to the problem. Both the involvement of the community and the education of individuals and institutions can be seen as attempts to create a demand for a quieter, more peaceful environment, and as means to empower people to gain the benefits of noise control. In contrast to the legal and regulatory approaches to date, these are strategies that seek to mobilize positive forces for prevention, rather than to react to problems after they have developed. While a distinction can be made between community involvement and education, the two are interrelated and overlapping strategies, and at this stage can only be discussed together, with examples drawn from a variety of contexts.

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In Most Cities, Noise Pollution Is a Big Problem And Affects the Quality of Life - IELTS Band 9 Essay

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Noise pollution in urban environments is escalating, significantly degrading quality of life. This uptick is largely attributable to increased urban density and outdated regulatory frameworks. To mitigate this, city authorities must implement stringent noise control measures and promote community awareness.

Primarily, the surge in noise pollution can be traced to the increasing concentration of population and machinery in cities. Urbanization brings a significant rise in vehicles, construction projects, and industrial activities, each adding substantially to the urban cacophony. For instance, the relentless roar of traffic has become a ubiquitous background noise in urban environments, regularly punctuated by the clamour of emergency sirens and the relentless din of construction equipment. The advancement towards 24-hour economies exacerbates this issue, as cities seldom experience periods of quiet, amplifying the stress on residents' mental and physical health. This relentless activity disrupts sleep patterns, heightens the incidence of stress-related ailments, and impairs overall urban liveability, placing additional strain on social and health services and eroding the quality of urban life.

Addressing this issue requires proactive governance by city authorities. Updated and rigorously enforced noise regulations, including zoning laws that segregate residential areas from industrial zones, are essential to shield inhabitants from severe noise pollution. Implementing congestion charges and promoting the use of public transport and bicycles have successfully reduced traffic noise in cities like Amsterdam and Singapore. These measures not only decrease noise pollution but also improve air quality. Additionally, investing in the soundproofing of public buildings and constructing noise barriers along highways can significantly lessen the auditory impact on citizens. Initiating community campaigns to raise awareness about the detrimental effects of noise and the importance of quiet zones can further cultivate a quieter, more harmonious urban environment.

In conclusion, the degradation of urban living conditions due to noise pollution necessitates immediate and innovative interventions by city authorities. By enforcing modernized regulations, enhancing infrastructure, and cultivating community involvement, cities can hope to quell the relentless rise of noise pollution.

Sample Essay 2

In many urban areas, the escalating problem of noise pollution significantly deteriorates quality of life. This essay contends that the rise in noise pollution can be attributed to urban expansion and inadequate regulatory frameworks, and it will argue that city authorities can mitigate this issue through stringent noise regulations and urban planning improvements.

The intensification of noise pollution in cities primarily stems from two factors: rapid urban expansion and the proliferation of transportation networks. Urban areas, burgeoning with skyscrapers and residential complexes, often suffer from construction noises that are incessant. Moreover, the density of these developments often means that such disturbances are widespread, affecting a large swath of the urban population. Transportation, too, contributes significantly to urban noise. The surge in private vehicle usage, coupled with outdated public transit systems, generates a constant background of traffic noise. For instance, cities like New York and Tokyo, despite having advanced public transportation, still grapple with traffic noise owing to their dense vehicular activity.

To combat the increasing noise pollution, city authorities can implement several effective strategies. First, the introduction of stricter noise regulations is imperative. These could include limits on noise levels at different times of the day, coupled with hefty fines for violations, which would compel businesses and individuals to adopt quieter operations. For example, in Zurich, regulations restrict nighttime noise, dramatically improving residents' quality of life. Additionally, enhancing urban infrastructure can also play a critical role. Investing in soundproofing public buildings and creating green buffer zones can significantly reduce the penetration of noise. Furthermore, promoting public transport and developing infrastructure for non-motorized transport, such as cycling lanes, can decrease reliance on private vehicles, thus reducing traffic noise.

In conclusion, while noise pollution is a growing urban issue, it is not insurmountable. By enforcing robust noise control regulations and improving city planning and infrastructure, authorities can significantly alleviate the acoustic burden on city dwellers. These measures not only promise a quieter environment but also enhance the overall urban quality of life.

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Essay on Noise Pollution

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In the modern world, the cacophony of sounds from vehicles, industrial activities, and urban development has become a constant backdrop to our lives. This relentless barrage of noise constitutes what we know as noise pollution, an environmental and public health issue that is often overshadowed by other forms of pollution but is equally potent and destructive. This essay delves into the depths of noise pollution, unraveling its causes, impacts, and potential solutions, aiming to shed light on an issue that is powerful in its ability to affect human health, wildlife, and the environment.

Noise Pollution

Noise pollution is defined as any unwanted or harmful sound that disrupts the natural balance and creates potential harm to human and animal life. The World Health Organization (WHO) has identified noise pollution as the second-largest environmental cause of health problems, just after the impact of air quality. From the incessant hum of traffic to the roar of airplanes overhead and the clamor of construction sites, noise pollution surrounds us, often so pervasive that many have become desensitized to its presence.

Causes of Noise Pollution

The sources of noise pollution are manifold and predominantly stem from urban development and human activities. Key contributors include:

• Transportation Systems: The roar of vehicles, trains, airplanes, and ships are amongst the most significant sources of noise pollution, especially in urban areas.
• Industrial and Construction Activities: Factories, construction sites, and mining operations generate substantial noise from machinery and heavy equipment.
• Urbanization: The growth of cities brings with it an increase in noise from commercial and residential areas, including sounds from electronic devices, entertainment venues, and human activities.
• Social Events: Concerts, festivals, and public gatherings can create high decibel levels, contributing to the noise landscape.

Impacts of Noise Pollution

The power of noise pollution lies in its pervasive ability to impact health and well-being, disrupt wildlife ecosystems, and contribute to societal issues.

Health Effects

Noise pollution is not merely an annoyance; it has profound health implications. Exposure to high levels of noise can lead to:

• Hearing Loss: Prolonged exposure to noise levels above 85 decibels can cause permanent hearing damage.
• Stress and Cardiovascular Issues: Noise acts as a stressor, triggering the release of stress hormones. Chronic exposure is linked to increased risks of high blood pressure, heart disease, and stroke.
• Sleep Disturbances: Noise can interrupt sleep patterns and reduce sleep quality, leading to insomnia and other sleep disorders.
• Cognitive Impairment: In children, noise pollution can hamper learning and memory, affecting academic performance and cognitive development.

Environmental and Wildlife Effects

Noise pollution extends its reach beyond human health, affecting the natural world in profound ways.

• Disruption of Wildlife: Animals rely on sound for communication, navigation, and predator-prey interactions. Noise pollution can interfere with these essential behaviors, leading to adverse effects on reproduction, feeding, and migration patterns.
• Ecosystem Imbalance: Excessive noise can alter the natural habitat, causing an imbalance in predator-prey dynamics and affecting biodiversity.

Societal and Economic Impacts

The repercussions of noise pollution also ripple through society and the economy, manifesting as:

• Decreased Productivity: Noise can distract and reduce efficiency, affecting workplace productivity and learning environments.
• Property Value Decline: Areas subjected to high levels of noise, such as those near airports or highways, often see a decrease in property values.
• Increased Healthcare Costs: The health issues associated with noise pollution lead to higher healthcare expenditures for individuals and governments.

Mitigating Noise Pollution

Addressing the issue of noise pollution requires a multifaceted approach, involving policy, technology, and community engagement.

Policy and Regulation

Effective noise pollution management starts with stringent regulatory frameworks that limit noise levels in residential, commercial, and industrial areas. Implementing noise standards for vehicles and machinery, along with zoning laws that separate residential areas from noisy industrial zones, are critical steps.

Technological Innovations

Advancements in technology offer promising solutions to reduce noise pollution. Quieter road surfaces, noise barriers, soundproofing materials in buildings, and the development of electric vehicles can significantly lower noise levels.

Community Engagement and Awareness

Raising awareness about the impact of noise pollution and promoting community involvement in noise reduction initiatives are essential. Simple actions, such as choosing quieter appliances, respecting noise ordinances, and planting trees to serve as natural sound barriers, can make a difference.

In conclusion, Noise pollution is an insidious force with the power to affect human health, disrupt wildlife, and impact societal well-being. Recognizing the seriousness of this issue is the first step towards mitigating its effects. Through a combination of policy intervention, technological innovation, and community action, we can attenuate the impact of noise pollution. By addressing this unseen power, we not only improve our quality of life but also protect the environment and ensure the health and well-being of future generations. In the fight against noise pollution, silence truly is golden.

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• Published: 29 November 2024

Investigation on multiple traffic noise near an airport and their effect on nearby residents

• Quanmin Liu 1 ,
• Kui Gao 1 ,
• Lizhong Song 1 ,
• Linya Liu 1 &
• Yunke Luo 2  

Scientific Reports volume  14 , Article number:  29680 ( 2024 ) Cite this article

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• Civil engineering
• Environmental impact
• Quality of life

This study investigates the impact of the noise radiated from airplanes, urban rail transit, high-speed railways, and urban roads on residents near an airport. The results showed that all respondents near the airport were highly annoyed with airplane noise, and some remain annoyed with the noise from the urban rail transit and high-speed railway connecting to the airport. The most detrimental aspect of transportation noise was sleeping disturbance. Transportation noise from 19:00 to 24:00 primarily caused the annoyance of surrounding residents. Airplane noise is the largest source of sound pollution in residences in the region adjacent to the elevated urban rail transit and airport. The insertion loss of vertical sound barrier with a height of 2.4 m at the points 25 m away from the track centerline is 6.9–8.6 dB, but the sound pressure level below 40 Hz is amplified owing to the structure-borne noise radiating from the barrier itself. The presence of sound barriers can reduce the high annoyance level from 24 to 8.2%.

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On the definition of noise

Introduction.

Multimodal transportation hubs that integrate railways, roadways, and aviation can facilitate the travel of passengers and movement of goods and improve the efficiency of transportation. As the scale of transportation demand and the corresponding infrastructure continue to expand worldwide, multimodal transportation hubs are becoming increasingly common. However, noise pollution caused by transportation around such hubs threatens the lives of nearby residents. The World Health Organization estimated that at least 100 million people in the EU are affected by road traffic noise, and in Western Europe alone at least 1.6 million healthy years of life are lost as a result of road traffic noise based on the assessment threshold specified in the Environmental Noise Directive of the European Union (EU) 1 . In the US, 7.8 million (2.4%) individuals were highly annoyed with aviation noise, while 5.2 million (1.6%) and 7.9 million (2.4%) were highly annoyed with rail and roadway noise, respectively, in 2020 2 . Data from the annual reports of the Ministry of Ecology and Environment of the People’s Republic of China show that the number of complaints about traffic noise in China increased markedly from 9,140 in 2014 to 195,000 in 2022. Noise pollution from traffic is an important environmental determinant of the health of the population 3 , 4 . Traffic noise, as an important source of noise pollution, has become a hot topic of government and public concerns 5 , 6 , 7 , 8 .

Traffic noise has a significant negative impact on health and well-being of citizens, including physical ailments and psychological problems. Many attempts have been made to explore the relationship between traffic noise and negative effects. Based on the meta-analysis it is found that road traffic noise was positively correlated with hypertension, and people exposed to traffic noise had a higher risk of cardiovascular disease 9 . The correlation between the exposure to road traffic noise and hypertension is quite strong when residents live in a house without triple-glazed windows, an old house and the bedroom window facing a street 10 . Additionally, long-term exposure to road traffic noise would significantly increase the risk of stroke and heart failure 11 . Railway noise can also have adverse effects on cardiovascular disease 12 . In Pisa of Italy and the Gyeonggi province of South Korea, railway noise was found to be more likely to cause fluctuations in blood pressure than road traffic noise 13 , 14 . The impact of airplane noise at night on cardiovascular disease included the rise in blood pressure, the increase of stress hormone, and the impairing of endothelial function 15 . The combination of different types of noises exacerbates the adverse effect on health. The combined exposure to airplane, road, and railway traffic noise results in the higher risk of depression than any of the separate traffic noise 16 .

In addition, prolonged exposure to transportation noise can cause sleep disturbances in people, and do harm to students’ ability to learn. It is reported that more and more residents are suffering from the sleep disturbance by the road traffic noise induced by urbanization 17 . Railway noise will improve the likelihood of sleep disruption 18 . The chronic sleep debt caused by long-term exposure to nocturnal railway noise deteriorates the cognitive performance for residents living along rail tracks 19 . The high-speed railway noise has caused some interference to students’ learning 20 . Students chronically exposed to airplane noise exhibited lower performance in reading comprehension 21 . The exposure to airplane noise increases the residents’ heart rates during the sleeping 22 . It is found that the airplane noise is the biggest threat to a sleep, followed by railway noise, and then road traffic noise 23 .

Noise annoyance can be considered an early warning sign of serious health risks because it has a much shorter developmental time than somatic diseases 24 . Therefore, the annoyance level experienced by people under the influence of noise must be accurately characterized. Typically, the annoyance level of people owing to traffic noise is described by exposure–response curves 25 . Many studies have focused on annoyance response under long- and short-term noise exposure conditions 26 , 27 , 28 , 29 . Brink et al. 24 built a mapping relationship between noise exposure and percentage highly annoyed under various individual noise sources (road, rail, or aviation) using a questionnaire survey and then characterized the exposure characteristics of noise by utilizing the intermittent ratio, suggesting that longer pauses are positive in reducing annoyance. The dose–response relationship suggests that higher levels of a type noise exposure, railway noise, induce higher levels of annoyance 26 , 27 . The road traffic noise in combination with rail traffic noise leads to an increase of the annoyance effect 28 . Noise caused by railway operations may exacerbate the annoyance level of residents 27 , 28 , 30 . Sociodemographic, psychosocial, and contextual factors also influence the annoyance level of affected individuals 31 .

The precise evaluation, assessment and monitoring of noise exposure are the prerequisite to reduce its adverse impact. Typically, this evaluation involves long-term average noise levels obtained through advanced measurement or simulation techniques 32 . Noise maps, as an effective tool for providing noise exposure in specific areas, have been widely applied and developed. Compared with the expensive method of obtaining noise maps through measurements in a regular grid of points, noise propagation models has been selected due to its economic advantage 33 . Changes in noise levels during long period and temporary variations in environmental noise 34 have highlighted the disadvantages of traditional “static” noise maps, and then dynamic noise maps have emerged. The dynamic noise map allows real-time monitoring on the impact of noise sources 35 . Tao et al. 36 investigate how different locations that individuals visited in their daily lives were associated with varying noise exposure and psychological responses from dynamic perspective. The internet of things has promoted the dynamic noise map through the development of wireless acoustic sensor networks 37 , 38 . However, noise monitoring requires the use of high-quality equipment 39 , and the cost remains high. The use of low-cost cameras and machine learning opens up a new possibility for the realization of noise maps over time 40 . Based on the large amount of data obtained from monitoring, the deep learning or artificial intelligence was used to predict the noise level 41 , 42 .

The measures to mitigate the impact of transportation noise can be taken on the source, path, or receiver. The control of source and transmission path are the widely used measures in transportation noise so far. The European Directive 2002/49/EC has been constructed as a policy instrument to assess and manage environmental noise 43 . Electric vehicles provide an opportunity for a reduction in environmental noise from vehicles 44 , which have reduced engine noise in the low speed range 45 . Low-noise pavement 46 , silent tires 47 and speed limit are used to mitigate the noise exposure level of road traffic. However, the aging or damage of tires and road surfaces will inevitably increase noise 48 . The reduction of running speed may cause the traffic congestion and low operational efficiency. As is well known, the higher speed of vehicle means the larger noise, especially for the wheel-rail noise 49 and aerodynamic noise 50 in railway systems. Therefore, the method to control noise in the propagation path is alternative when noise reduction at the source fails to achieve the desired goal or is difficult to deal with. The sound barrier has become the most effective measure used in the suppression of transportation noise 51 .

The sound pressure level like the day-evening-night level 52 has been used to evaluate human physiological or psychological responses to traffic noise. The psychoacoustic and noise indices from the sound pressure level of transportation noise were proposed for noise evaluation on environmental noise exposure 53 . Nevertheless, sometimes the increase in the sound pressure level plays an important role in influencing people’s perceptions 54 . The spectral characteristic of noise is also crucial to analyze human responses 55 , 56 . Recently, the scientific community also has moved its attention towards realizing a broader spectrum of sound exposure features, and not only the annual average. Peak level and variation over time, impulsivity of events, frequency distribution, psycho-acoustics parameters can all have a significant influence on nuisance perception, and citizens are known to complain more about single high levels rather than average exposure 57 . Therefore, the variation in the human exposure–response induced by the diverse spectral characteristics of various traffic noises is still worthy of discussion.

The objective of the present study is to investigate the annoyance and spectral characteristics of airplanes, high-speed railways, elevated urban rail transit noise, and exposure of different noise sources. Additionally, the ability of sound barriers to mitigate noise from urban rail transit viaducts was elucidated, and the relationship between the sound barriers and the annoyance response of residents along the viaduct was demonstrated. This paper is structured as follows. Section  2 presents the survey, and noise tests which consists of the testing instrument, the description of measuring point layout, and the noise evaluation method. Section  3 analyzed the results of the survey and noise test. The annoyance levels, time periods, and activities of residents affected by airplane, urban rail transit, high-speed railway, and urban road noises are demonstrated. The sound source characteristics and dose-response relationships of four sound sources are given. The effects of sound barriers in reducing noise and high annoyance are also quantified. Finally, Section 4 gives the conclusions.

Survey and field tests

Survey on the impact of noise on residents.

A questionnaire survey is one of the most commonly used methods for assessing the subjective experiences of residents affected by transportation noises. In this study, a questionnaire survey was conducted to evaluate the annoyance responses of neighboring residents influenced by traffic noise. The design of the questionnaire was based on the best practice guidelines for noise annoyance developed by the International Commission on the Biological Effects of Noise 58 , guidelines from ISO/TS 15,666: 2021 59 , and the Chinese Standard GB/T 42,473 − 2023 60 . Owing to questionnaire length and cost constraints, and to make it easier to use, a 5-point scale, which corresponds to an 11-point numeric scale, was used to indicate the annoyance level 61 . Factors affecting the annoyance rate, such as different types of transportation noise sources, distance from the noise source, sound barriers, and life pressures, were considered in the questionnaire. Gender, age, education level, and noise sensitivity related to annoyance level 62 , 63 , 64 , 65 , 66 were also included. The questionnaire is shown in Table S1 .

This questionnaire investigated the relationship between traffic noise and the annoyance responses of residents near airports and urban railway transit/urban roads. The airplane noise is a particular nuisance on take-off and landing 67 , which seriously impacts nearby residents. Residents reacted strongly to disturbances in airplane noise. Simultaneously, the residential areas near the international airport also receive the noise from the urban rail transit and high-speed railway. Therefore, the questionnaire was used to investigate the degree of annoyance among residents under the influence of multiple transportation noise sources. The questionnaire survey was conducted during on-site visits. After checking and eliminating invalid questionnaires, 200 valid questionnaires were obtained. Photographs of the onsite questionnaire survey are shown in Fig.  1 .

Photos of questionnaire survey.

Test 1 is used to determine the characteristics of several noise sources and it is located in Village 1 near an airport in China, where the residents are plagued by airport, urban rail transit, and high-speed railway noise. Test 2 and Test 3 are used to evaluate the reduction performance of upright sound barriers on urban rail transit noise. Test 2 and Test 3 are located in a section with sound barriers and without vertical sound barriers in an elevated urban rail transit line. The locations of the three tests are shown in Fig.  2 . It should be noted that this test plan is determined based on the ISO 3095: 2013 68 and the Chinese Standard GB 12525-90 69 .

Satellite map 70 of measurement point locations and surrounding noise sources (Baidu Maps (Version: V19.1.0) [Web Application Software]. URL: https://map.baidu.com . (2023)).

Testing instrument

The testing equipment included a 24‒channel data acquisition device and free-field microphones which were calibrated before the test. When the equivalent continuous sound pressure level during the duration of transportation noise was calculated, the integration time of airplane, urban rail transit, and high-speed railway noise was 7.6 s, 8.7 s, and 20 s, respectively. The sampling frequency range is 25,000 Hz.

Measuring point layout

Assessing people’s actual responses to noise from either outdoor or indoor noise levels is unreasonable 71 . Therefore, Test 1 was conducted to simultaneously obtain actual noise levels inside and outside a residence and assess the difference between indoor and outdoor noise. The spectra and overall sound pressure levels of multiple transportation noises were obtained during this field test.

As shown in Fig.  3 , measurement points NP1 to NP5, located outside the residential sites and close to the urban rail transit viaduct in Location 1, were used to assess outdoor transportation noise. Additionally, five measurement points were arranged at Location 2, inside and outside the residence, to measure the sound pressure levels of indoor and outdoor noise. The second-floor height of the residence is 3.3 m. Measurement points N1 and N2 were located on the first floor of the residence, 1.2 m above the outdoor and indoor floors, and N3 (outdoor) and N4 (indoor) were located 1.2 m above the second floor of the residence. N5 was located at a distance of 7.8 m above the ground level and was used to assess the outdoor airplane noise. Microphones N5 and NP5 were fixed vertically to the fiber rods to obtain the sound pressure of the airplane noise. Windows and door were closed during the tests. The test photographs are shown in Fig.  4 .

Layout of noise measuring points in a residential area (unit: m).

Field test in residential areas.

The layouts of the noise measurement points of the viaduct sections with and without sound barriers were identical in Test 2 and Test 3, as shown in Figs.  5 and 6 . The running speed was 73 km/h when six-car B-type subway trains passed through both test sections. Because the noise of elevated urban rail transit is dominated by wheel-rail noise and bridge structure-borne noise, measurement points N1 to N3 were arranged in the cable support next to the rail to acquire the wheel-rail noise. N5 to N6 were placed beneath the box girder bottom plate to measure the bridge structure-borne noise. To collect the comprehensive noise of the urban rail transit viaduct and study its diffusion, noise measurement points N7 to N11 and N12 to N16 were arranged at 7.5 m and 25 m away from the track centerline, respectively.

Noise measurement points above the bridge deck (unit: m).

Layout of noise measurement points for the urban rail transit viaduct (unit: m).

The viaduct contains 30 m simply supported concrete box-girders, with a deck slab width of 9.3 m, bottom slab width of 4.0 m, and girder height of 1.8 m; the spacing of the track centerlines of the double-track viaduct is 4.0 m. The height of the bottom of the girder for the vertical sound barrier section was 2.4 m from the ground, whereas that of the section without a sound barrier was 3.8 m. The height of the vertical sound barrier was 2.4 m, the thickness of the polycarbonate board (PC board) was 10 mm, and the thickness of the sound-absorbing board was 128 mm. Photographs of the field tests are shown in Fig.  7 .

Noise measurement points on the box-girder side. (a) Test 2 (b) Test 3.

Noise evaluation method

The sound pressure data during the train passing time t is extracted for the calculation of equivalent continuous sound pressure level 68 , as shown in Eq. ( 1 ).

where, L pAeq, T is the A-weighted equivalent continuous sound pressure level in dB; T is the measurement time interval; p A (t) is the A-weighted instantaneous sound pressure at running time t in Pa; p 0 is the reference sound pressure; p 0  = 20 µPa.

Results analysis

Noise annoyance assessment.

The sample distribution of the samples from the 200 valid responses is listed in Table S2 . Residents in the vicinity of airports and elevated urban rail transit suffer from airplane, elevated urban rail transit, high-speed railway, and urban road noise. Because of the large overlap between residents near the urban rail transit viaduct and urban roads, the two sources are assumed to share identical samples.

The impacts of airplanes, urban rail transit, high-speed railway, and urban road noise on residents near the airport are shown in Fig.  8 . The “Very” and “Extremely” annoyed people accounted for the “highly annoyed” number 59 . Airplane noise had the greatest impact on the interviewed residents, and 100% of the residents involved in the survey experienced a high level of annoyance. Urban rail transit and high-speed railway noise also had a significant impact on the residents who completed the questionnaire, and the percentages of residents corresponding to a high annoyance degree were 44.44% and 16.67%, respectively. According to the survey, urban road noise has little impact on residents near airports. Thus, airplane noise was considered the dominant noise pollution source for residents near airports.

Responses of the residents near the airport to multiple transportation noise. AP: Airplane, URT: Urban rail transit, HSR: High-speed railway, UR: Urban road.

Of the respondents, 94.44% reported that their sleep was disturbed by the airplane noise. Sleep was the most disturbed activity, followed by studying and work. Most respondents indicated that the period of annoyance was the evening, among which 66.67% of the respondents were annoyed from 19:00 to 21:00 and 55.56% from 21:00 to 24:00. Some residents near the airport were disturbed by noise at other times of day. Due to the residents’ annoyance of multiple sources, 44.44% of the respondents near the airport complained about transportation noise, with 22.22% complaining at least four times. Furthermore, according to the feedback, 72.22% of the respondents think that government-sponsored residential relocation is the best solution to the noise problem in the region close to the airport.

For residents near urban rail transit viaducts, the noise induced by trains running on the viaduct and cars running on urban roads have the greatest impact on their lives. Figure  9 shows that the residents near the elevated urban rail transit were the least annoyed with airplane and high-speed railway noise because these two sources are sufficiently far from the respondents. Therefore, urban rail transit viaducts and roads were their primary sources of noise. The percentage of respondents who were highly annoyed or annoyed with urban rail transit viaduct noise reached 53.30%. In addition, 46.70% of the respondents said that they were annoyed with urban road noise.

Responses of the residents near the urban rail transit viaduct to multiple transportation noise.

Sleep was also the most interrupted aspect of transportation noise, as reported by 50.56% of the respondents. Unlike the circumstances in regions near airports, residents near viaducts are affected by transportation noise in many ways, including sleep, study, mental state, and conversations. The reason for this phenomenon may be that the effects of airplane noise on talking, studying, and mood are negligible when sleep is deeply disturbed by airplane noise. The main period of transportation noise that annoyed the residents near the viaduct was also from 19:00 to 24:00. Because the sound pressure level of elevated urban rail transit and urban road noise beside the viaduct is lower than airplane noise near the airport, the proportion of residents’ complaints was significantly reduced. However, the number of resident complaints was also considerable because of the high density of residents living near urban rail transit viaducts. To guide the design and implementation of noise reduction measures for urban rail transit viaducts, the factors affecting the annoyance of residents were clarified. The correlations between the factors and annoyance levels were determined using logistic regression 28 . The dependent variable produced either high annoyance or not under the influence of these factors. Therefore, a binary logistic regression analysis was used to investigate the relationship between these factors and high annoyance. The sign of the regression coefficient determines the positive or negative correlation between the annoyance level and the independent variable. If the regression coefficient is positive, an increase in the factor increases the proportion of high annoyance in the population, and vice versa. The odds ratio, as an estimation of risk 29 , is the exponential power of the regression coefficient, and indicates the corresponding magnitude of change in the dependent variable when the independent variable increases by one unit. The significance level in hypothesis testing refers to the probability or risk that the original hypothesis will be rejected if correct. This value is frequently considered as 0.05, indicating that the probability of being correct is 95% when the original hypothesis is accepted.

Through binary logistic regression analysis, the correlation level of each factor with a high annoyance level under a confidence interval of 95% was obtained, as shown in Table  1 . The distance from the residence to the viaduct, the residents’ sensitivity to noise, and sound barriers had a significant correlation with the high annoyance level because their significance level was < 0.05. In contrast, the annoyance level was not sensitive to other factors. Similarly, for urban road noise, the distance between the residence and the road, residents’ sensitivity to noise, and life pressure were correlated with a high annoyance level under a confidence interval of 95%, while the other factors did not change the annoyance level significantly, as shown in Table  2 .

Noise investigation of multiple sources

Due to the involvement of noise source superposition in multi-source mixed testing scenes, this section discusses independent sound sources and combined noise sources separately.

Independent sound source

By analyzing the data of Test 1, the A-weighted spectral characteristics and overall sound pressure levels of multiple transportation noises were obtained; Figs.  10 and 11 show the airplane noise. The overall sound pressure levels at N1 and NP1, which were 1.2 m above the ground, reached 77.2 and 77.8 dB(A), respectively, and were less than those at the other outdoor points due to the shielding of the ground building and plants to the airplane noise. For NP2–NP5 at Location 1, the peak value in the frequency domain was approximately 73 dB(A) and the dominant frequency ranged from 500 to 3000 Hz. The overall sound pressure levels at these points exceeded 80 dB(A). Furthermore, the overall sound pressure levels of indoor noise on the first and second floors were 62 (N2) and 63.8 dB(A) (N4), respectively. Due to the shielding effect of the walls and windows of the houses, a reduction of 15.3 and 16.3 dB(A), respectively, were achieved compared with the outdoor measurement points at the same height. From the outdoor airplane noise test results for N5 and NP5, the airplane noise spectra at Locations 1 and 2 exhibited the same trend.

Outdoor noise at Location 1 (near the viaduct) from an airplane.

Indoor and outdoor noise at Location 2 from an airplane.

The spectra and overall sound pressure levels of the urban rail transit viaduct noise at Locations 1 and 2 are shown in Figs.  12 , 13 , 14 and 15 . The frequency of the noise peak generated by the elevated urban rail transit system was approximately 800 Hz. The peak sound pressure levels at the measurement points approximately 93 m from the viaduct were 58–60 dB(A), and the peak of the outdoor noise at Location 2, which was 196 m from the urban rail transit, was 46–47 dB(A) in the frequency domain. The difference between the radiated noise of the elevated urban rail transit induced by a train running in two directions was less than 1.3 dB(A). The indoor noise was 12.7–15.5 dB(A) less than the corresponding outdoor noise in Location 2 owing to the shielding of walls and windows. The indoor noise at N4 on the second floor was 2.8–4.8 dB(A) larger than that at N2 on the first floor due to the shielding of ground building to the high-frequency noise.

Outdoor noise from the urban rail transit induced by a train running through the nearer track.

Outdoor noise from the urban rail transit induced by a train running through the farther track.

Indoor and outdoor noise from the urban rail transit induced by a train running through the nearer track.

Indoor and outdoor noise from the urban rail transit induced by a train running through the farther track.

Indoor and outdoor background noise at Location 2.

The indoor and outdoor background noises at N1–N5 in Location 2 are shown in Fig.  16 . A comparison of Figs.  14 and 16 shows that the indoor and outdoor noise of the residence increased by 4.5–6.3 dB(A) owing to the noise of the elevated urban rail transit. The inside and outside environments of the residence at Location 2 were polluted by urban rail transit noise.

Figures  17 and 18 show the spectra and overall sound pressure levels of the high-speed railway noise at both locations. The peak frequency of the high-speed railway noise at these points was approximately 630 Hz and the peak sound pressure level reached 70 dB(A). The sound pressure level of high-speed railway noise in the range of 500–630 Hz was much greater than that in other frequency bands. The overall sound pressure level of outdoor noise at Location 1 near the viaduct reached 59.5–72.2 dB(A). The overall sound pressure levels of the indoor noise at N2 and N4 were 51.4 and 50.9 dB(A), respectively, which are 10.8 and 16.1 dB(A) lower than those of the outdoor noise near the residence, respectively.

Outdoor noise from the high-speed railway.

Indoor and outdoor noise from the high-speed railway.

The test results of the airplane, urban rail transit, and high-speed railway noise at N3 and N4 in Location 2 of Test 1 are shown in Fig.  19 , where the shaded portion is the envelope of all test results and the solid line is the mean value of the measured sound pressure level. The sound pressure level of the airplane noise was the highest. The dominant frequency ranges of airplane and urban rail transit noise were quite broad, making it challenging to control these two types of noise. The variability of airplane and high-speed railway noise was relatively small, but the uncertainty of urban rail transit noise was significant.

Figure  20 shows the indoor and outdoor sound pressure levels of the airplane, urban rail transit near the track, and high-speed railway noise, respectively. Based on this figure, the sound pressure level of airplane noise was the highest, followed by high-speed railway noise and urban rail transit viaduct noise.

Measured sound pressure levels inside and outside the residence.

Indoor and outdoor noise from various sound sources.

As shown in Fig.  21 , the transmission loss ( TL ) from the outdoor to the indoor point of multiple transportation noise mainly occurs in the frequency bands above 50 Hz, and the outdoor noise is reduced by 10.8 to 16.3 dB(A) due to the shielding of walls or windows, which indicates that these barriers have a good noise reduction effect on the noise sources. Notably, the TL of the high-speed railway noise on the first floor was much lower than that on the second floor. This may be the reason why no obstacle is in the higher position between the measurement point on the second floor and the high-speed railway, except for the propagation medium air; this measurement point was mainly affected by high-frequency wheel-rail noise. However, buildings and vegetation around the ground have sound attenuation. Compared with the TL of urban rail transit and high-speed railway noise, the TL of airplane noise was the largest. Furthermore, airplane noise was the largest source of sound pollution in residential rooms.

Transmission loss between indoor and outdoor noise (1 F: the first floor, 2 F: the second floor).

Mixed sound source

There is interaction between sound sources, and there may be overlap in certain frequency bands. Therefore, based on the results of on-site testing, the noise exposure was analyzed when multiple sound sources coexist. The airplane noise and its mixed noise with urban rail transit (AP + URT) noise or high-speed railway (AP + HSR) noise at NP1 and NP5 measurement points are shown in Figs.  22 and 23 . In Fig.  22 , the peak value of high-speed railway noise occupies a dominant position when airplane noise and high-speed railway noise coexist. When airplane noise and urban rail transit noise coexist, the low-frequency band is dominated by urban rail transit noise, and the high-frequency band is dominated by airplane noise. In Fig.  23 , due to the fact that the influence of bridge structure-borne noise on NP5 is smaller than that of NP1, the dominant low-frequency noise of the mixed noise of airplane and elevated rail transit is relatively reduced compared to airplane noise. The difference of overall sound pressure levels between airplane noise, airplane noise combined with high-speed railway noise, and airplane noise combined with urban rail transit noise is not significant, but the overall sound pressure level of mixed noise is slightly lower, which may be due to the counteraction effect between the noises.

Comprehensive noise of measuring point NP1.

Figures  24 and 25 show the mixed noises at measurement points N12 and N16 in Test 3. Compared with Figs.  22 and 23 , there are no regularity in the differences between urban rail transit noise and various mixed noises in Figs.  24 and 25 . This indicates that the sound source (airplane noise or high-speed railway noise) has little influence on mixed noise because it is far away from the measurement points in urban rail transit section.

Comprehensive noise of measuring point N12.

Comprehensive noise of measuring point N16.

Noise reduction evaluation of sound barrier

For elevated urban rail transits, sound barriers 72 are widely used to relieve the impact of transportation noise on residents. The structural forms of sound barriers are diverse, including vertical, semi-enclosed, and fully-enclosed. Among them, the fully-enclosed sound barrier has the best noise reduction effect, but it has the problems of high cost and relatively large secondary structural noise 73 , 74 , so its application is relatively limited. Vertical sound barrier is the most common structural forms, and a deep understanding of their noise-reduction characteristics is important in the design of elevated urban rail transit. Herein, the noise reduction effect of vertical sound barriers is characterized by insertion loss ( IL ) 75 , as shown in Eq. ( 2 ).

where, p before and p after are the sound pressure of the same receiver point before and after installation of sound barriers in Pa, respectively. The IL is the difference of sound pressure level before and after installation of sound barriers in dB, which directly reflects the noise reduction effect of the sound barrier. Due to the inconsistent sound pressure levels of sound sources with and without sound barrier cross-sections, it is impossible to directly calculate IL using Eq. ( 2 ), so an analysis of the TL is introduced to indirectly obtain the value of IL . The TL is the difference between the sound pressure level of the trackside measurement point at the noise source position and the wayside measurement point at the noise receiver position, as shown in Eq. ( 3 ).

where, L a and L b represent the sound pressure levels measured at noise source and noise receiver position in dB(A), respectively.

In the formula, TL 1 and TL 2 are the transmission losses of the section with and without sound barriers, respectively; L 1 and L 3 represent the sound pressure levels measured at the trackside measurement points of the section with and without sound barriers, respectively; L 2 and L 4 are the sound pressure levels measured at the wayside measuring points of the section with and without sound barriers, respectively.

Figure  26 shows the test results for the trackside noise in the two sections. M1 and M2 are the average values of the overall sound pressure levels at three trackside noise measurement points in the two sections and are used as the source intensity of the elevated urban rail transit noise. Evidently, the sound source intensity of the urban rail transit viaduct in the section with a sound barrier was 4.7 dB(A) larger than that in the section without a sound barrier, owing to the reverberation of the wheel-rail noise. In addition, the spectral characteristics of the source intensity of the two sections differed; therefore, the IL of the sound barrier cannot be calculated directly using the sound pressure levels of the corresponding bridge-side points of the two sections. Hence, the TL between the trackside noise measurement points and the measurement points 7.5 or 25 m away from the track centerline was first calculated and then used to obtain the IL of the vertical sound barrier.

Test results of trackside noise at the sections with and without a vertical sound barrier (SB).

Figures  27 and 28 show the TL from the trackside points to N7–N16 on the side of the box girder with and without the sound barrier. The TL at the measurement points 7.5 m from the track centerline was 18.2–29.7 dB(A) for the sound barrier section and 10.2–22.7 dB(A) for the section without the sound barrier. Furthermore, the TL from the trackside points to the points 25 m away from the track centerline were 28.1–34.0 dB(A) with the barrier and 19.6–27.1 dB(A) without the barrier.

Transmission loss of the noise in the box-girder side of the vertical sound barriers section.

Transmission loss of the noise in the box-girder side of the section without the vertical sound barriers.

Figure  29 shows the IL at N7 to N11 on the box-girder side, 7.5 m away from the track centerline. The IL trend at each measurement point was not consistent in the frequency domain. In particular, the IL at N7–N11 varied significantly in the frequency band above 400 Hz. The IL in the frequency band above 40 Hz was positive, indicating that the vertical sound barriers had a good noise reduction effect in the middle- and high-frequency bands. However, a negative IL means that the sound barrier does not reduce the noise from the urban rail transit below 40 Hz, but instead amplifies the noise. This may be caused by structure-borne noise radiating from the sound barrier. The overall IL at N7–N11 on the box-girder side were between 7.0 and 15.9 dB. The IL at N9 was the largest, with a value of 15.9 dB, among the points from N7 to N11. The sound pressure level of N7, located 1.2 m above the ground, was dominated by bridge structure-borne noise, so its IL was the least among the points 7.5 m away from the track centerline. The IL at N11 was also relatively small because the position of N11 was higher than the top of the sound barrier.

The IL of measurement points N12–N16, 25 m from the track centerline, is shown in Fig.  30 . The overall IL at N12–N16, 25 m away from the track centerline on the box-girder side, was between 6.9 and 8.6 dB. The IL at N12 was close to that at N7 because the sound barriers mainly reduced the wheel-rail noise, and the bridge structure-borne noise was dominant at these two measurement points. The IL spectral curves of the measurement points 25 m away from the track centerline on the box-girder side were similar, except for N12.

Insertion losses of measurement points 7.5 m away from the track centerline on the box-girder side.

Insertion losses of measurement points 25 m away from the track centerline.

Dose-response relationship

Based on the above analysis, it can be seen that residents react differently to different traffic noise sources. It is not enough to analyze the characteristics of the noise source, but it is also necessary to introduce other acoustic metrics for evaluating annoyance. The A-weighted day-evening-night noise level L den and night noise level L n are used in the assessment of long-term noise levels 76 , 77 . L den is expressed in decibels and calculated according to Eq. ( 5 ) 43 .

where L d , L e , and L n are the A-weighted average sound levels for the day from 6:00 a.m. to 6:00 p.m., the evening from 6:00 p.m. to 10:00 p.m.), the night periods from 10:00 p.m. to 6:00 a.m., respectively. These time intervals are not fixed and may vary from country to country 78 .

The short-term noise levels obtained from this test are used to estimate the indicators of long-term noise levels ( L d , L e , L n ) calculated by Eq. ( 6 ) and then the A-weighted day-evening-night noise level ( L den ) is estimated according to Eq. ( 5 ). The noise levels of hours were obtained from the measurement over 5 days. The sound pressure data during the transportation vehicles or airplanes passing through time period t and background noise sound pressure for these four types of traffic noise were extracted from the test noise data. The day, evening and night noise levels ( L d , L e , and L n ) for these four noise sources were calculated based on the operation frequency and the overall sound pressure level of transportation vehicles or airplanes and background noise levels during three time periods.

where, L i is L d , L e , L n , representing day, evening, and night noise level, respectively. L j is the equivalent continuous A-weighted sound pressure level of time period j. N is the number of time periods.

The calculated the A-weighted day-evening-night noise levels under different sound sources are shown in Table  3 . L den (indoor) and L den (outdoor) are the day-evening-night noise level of indoor and outdoor noise radiated from various noise sources, respectively. In the vicinity of the airport, despite the influence of urban roads, high-speed railways, and elevated urban rail transit noise, airplane noise remains the largest source of noise. L den in outdoor caused by airplane noise reaches 76 dB(A), causing 100% highly annoyed among surrounding residents. A significant difference, 19.4 dB(A), was found between indoor noise and outdoor noise radiated from airplane. In the area near the elevated urban rail transit, the L den of urban road noise is 3 dB(A) less than that of elevated urban rail transit, but the percentage of high annoyance level is the same. The L den of urban rail transit in the vicinity of the airport and away from the airport is equivalent in magnitude, but the percentage of high annoyance of the former is 34% high than that of the latter, which may be due to the accumulation of airplane noise.

Table  1 indicates that the presence of sound barriers can reduce the high annoyance level, which needs a quantitative analysis. In order to further determine the necessity of setting up sound barriers, Table  4 provides the L den and high annoyance levels for measuring points N12 and N16. L den (no SB) and L den (SB) are the day-evening-night noise level at the section without and with sound barriers, respectively. The L den of N16 measurement point compared to N12 indicates that the noise exposure above the top surface of the sound barrier is higher than that below the top surface. This may result in sound barriers having no noise reduction effect on residents living in high-rise buildings. The presence of sound barriers can indeed reduce the L den in residential areas by 0.6 and 1.8 dB(A), resulting in a decrease in high annoyance levels from 24 to 8.2%. This result indicates that the sound barrier has good application value.

Conclusions

The transportation noise in a region near an international airport connected to an urban rail transit viaduct was investigated in this study. A questionnaire survey was conducted on the annoyance level of residents suffering from transportation noise in this region, and the sound pressure levels of airplanes, urban rail transit viaducts, and high-speed railway noises were measured. The influence of noise radiating from airplanes, elevated urban rail transit, high-speed railways, and urban roads on surrounding residents was investigated, and the noise reduction effect of the vertical sound barrier was analyzed. All interviewed residents near the airport were highly annoyed with airplane noise, and some were also annoyed with the noise from the urban rail transit and high-speed railway connecting to the airport. Sleep was the most frequently interrupted activity due to transportation noise. Transportation noise during 19:00–24:00 most affected the residents near the airport and urban rail transit. The distance from residences to the viaduct, sensitivity of residents to noise, and sound barriers were strongly correlated with a high annoyance level for urban rail transit noise under a confidence interval of 95%. Meanwhile, the annoyance level of urban road noise is dependent on the distance between the residence and the road, noise sensitivity, and life pressures. Airplane noise remains the largest source of sound pollution in residences near the elevated urban rail transit and airport. The broad dominant frequency ranges of airplane and urban rail transit noise make it challenging to control these two types of noise. The source intensity of the elevated urban rail transit in the barrier section is 4.6 dB(A) higher than that in the section without a sound barrier owing to the reverberation of wheel-rail noise. The insertion loss of the urban rail transit noise at 7.5 m and 25 m away from the track centerline was 7–15.9 dB and 6.9–8.6 dB, respectively, indicating that above 40 Hz, the vertical sound barrier has a good noise reduction effect on the urban rail transit viaduct. The dose-response relationship indicates that the L den of outdoor noise is 19.4 dB(A) higher than indoor noise radiated from airplane. The presence of sound barriers can reduce the L den in residential areas, resulting in a decrease in high annoyance level from 24 to 8.2%. This study shows that the operation of transportation lines brings many negative impacts to the surrounding residents. The location, later operation and maintenance of transportation lines should be considered comprehensively to reduce traffic noise.

Data availability

The data within the paper are available from the authors upon request. Requests for data should be addressed to Song, L. Z. (E-mail addresses: [email protected]).

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Acknowledgements

This study was financially supported by the National Natural Science Foundation of China (Grant numbers 52068030, 52372328, and 52378450), the China Postdoctoral Science Foundation (Grant Numbers 2023T160214 and 2023M731077), the Technology Research and Development Program of China Railway Corporation (Grant Number P2022Z003-2), and the 2024 Postgraduate Innovation Special Foundation of Jiangxi Province (Grant Number YC2024-B202).

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Quanmin Liu: Conceptualization, Funding acquisition, Investigation, Methodology, Project administration, Supervision, Validation, and Writing - review & editing. Kui Gao: Conceptualization, Data curation, Formal analysis, Investigation, Methodology, Visualization, and Writing - original draft. Lizhong Song: Funding acquisition, Investigation, Project administration, Resources, and Writing - review & editing. Linya Liu: Project administration, Supervision, and Writing - review & editing. Yunke Luo: Conceptualization and Writing - review & editing.

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Natural soundscapes enhance mood recovery amid anthropogenic noise pollution

Roles Conceptualization, Formal analysis, Investigation, Methodology, Writing – original draft

Affiliation School of Applied Sciences, College of Health, Science and Society, University of the West of England, Bristol, United Kingdom

Roles Methodology, Supervision, Writing – review & editing

Affiliation School of Health and Social Wellbeing, College of Health, Science and Society, University of the West of England, Bristol, United Kingdom

Roles Methodology, Writing – review & editing

Affiliations School of Health and Social Wellbeing, College of Health, Science and Society, University of the West of England, Bristol, United Kingdom, Centre for Human Psychopharmacology, Swinburne University of Technology, Melbourne, VIC, Australia

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* E-mail: [email protected]

• Lia R. V. Gilmour, 
• Isabelle Bray, 
• Chris Alford, 
• Paul R. Lintott

• Published: November 27, 2024
• https://doi.org/10.1371/journal.pone.0311487
• Peer Review
• Reader Comments

In urbanised landscapes, the scarcity of green spaces and increased exposure to anthropogenic noise have adverse effects on health and wellbeing. While reduced speed limits have historically been implemented to address traffic safety, their potential impact on residents’ wellbeing, especially in relation to engagement with natural soundscapes, remains understudied. Our study investigates the influence of i) natural soundscapes, including bird song, and ii) the addition of traffic noise to natural soundscapes at two speeds (20 mi/h and 40 mi/h) on mood. We found that natural soundscapes were strongly linked with the lowest levels of anxiety and stress, with an increase in stress levels associated with mixed natural soundscapes with the addition of 20 mi/h traffic noise and the highest levels with 40 mi/h traffic noise. Higher levels of hedonic tone, indicative of positive mood, was noted with natural soundscapes, but diminished when combined with 40 mi/h traffic noise. Our results show that anthropogenic soundscapes including traffic sounds can mask the positive impact of natural soundscapes including birdsong on stress and anxiety. However, reducing traffic speeds in cities could be a positive intervention for enhancing access to nature. Technological solutions, such as the widespread adoption of hybrid and electric vehicles, and urban planning strategies like integrating green spaces into transit routes, offer potential opportunities to mitigate the impact of noise pollution and benefit humans in urban environments.

Citation: Gilmour LRV, Bray I, Alford C, Lintott PR (2024) Natural soundscapes enhance mood recovery amid anthropogenic noise pollution. PLoS ONE 19(11): e0311487. https://doi.org/10.1371/journal.pone.0311487

Editor: Yuan Zhang, Shenyang Jianzhu University, CHINA

Received: March 8, 2024; Accepted: September 19, 2024; Published: November 27, 2024

Copyright: © 2024 Gilmour et al. This is an open access article distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Data Availability: All relevant data are within the paper and its Supporting Information files.

Funding: The author(s) received no specific funding for this work.

Competing interests: The authors have declared that no competing interests exist.

Introduction

Since the industrial revolution, many landscapes have become increasingly characterised by their anthropogenic footprint and this has profoundly affected both human health and wellbeing, as well as ecological communities [ 1 ]. Access to nature can lead to reduced risk of obesity and dementia, increase life satisfaction, aid stress recovery and provide restorative benefits (e.g. [ 2 – 5 ]. Furthermore, faced with global biodiversity and climate crises, increasing connection between people and nature is also important for improving engagement in environmental conservation actions [ 6 ]. Consequently, better understanding of the relationship between humans and nature in urban areas is vital.

Beneficial effects of nature may depend on an individual’s background, perception of biodiversity, its restorative potential and the senses used to perceive it [ 5 , 7 ]. Recently, various soundscape playback studies have examined the potential impacts of exposure to natural sounds (reviewed by [ 8 ]) and have shown that natural soundscapes, can aid health recovery and attention restoration in participants [ 9 – 14 ]. Studies have reported both physiological and psychological benefits to health from listening to natural sounds or soundscapes [ 8 ]. For example, natural sound exposure has been shown to lower blood pressure, heart and respiratory rates, as well as self-reported stress and anxiety [ 8 , 13 , 15 ]. Listening to natural sounds can also improve attention restoration and increase cognitive performance [ 8 , 13 , 14 ]. Responses to nature, including natural soundscapes, may also be dependent on factors such as age, sex and socio-cultural experience e.g. childhood connection to nature [ 11 , 16 , 17 ], though more research is needed to understand and tease apart the influence of these factors.

Conversely, anthropogenic soundscapes, such as those including traffic or aircraft noise, can have negative effects on human health and wellbeing with physiological and psychological effects recorded across the literature [ 18 – 22 ]. Exposure to sounds made by traffic infrastructure (including rail, road and air traffic noise) has been recorded to increase the risk of depression [ 21 ], severe anxiety [ 22 ] and physiological stress responses such as increase in cortisol levels [ 18 ]. Indeed, psychological effects of listening to traffic are likely to be caused by direct adverse impacts and changes in the central nervous system, causing for example changes to brain tissue and neuroinflammation [ 23 ]. Long-term effects of exposure to traffic noise also include increased instances of cardiovascular disease, risk of stroke, diabetes, hypertension and loss of hearing [ 19 ]. Higher traffic speeds are associated with higher noise pollution and perceived annoyance levels in people exposed to the sounds [ 24 ]. However, to our knowledge there has been no study to date that has examined the impact of lowering road traffic speeds on the sonic environment people are exposed to in urban environments and how this affects wellbeing.

Historically, reduced speed limits have been introduced to slow traffic and reduce the number and severity of road traffic collisions. International agencies including the World Health Organisation, World Bank and the Organisation for Economic Co-operation and Development have promoted the implementation of reduced speed limits across residential roads (e.g. reducing speed limits in the UK from 30 mi/h down to 20 mi/h, equating to a reduction of 50 to 30 km/h in equivalent traffic regimes). Although reduced traffic speeds are strongly associated with reductions in road traffic casualties (e.g. [ 25 ]), the current move towards lower speed limits is only in part powered by the injury prevention agenda. Reduced speed limits lessen noise pollution, as well as having proportionately larger positive impacts for poorer communities which suffer from higher levels of traffic pollution [ 26 ], thereby reducing inequalities in health. Also significant is the desire to reduce obesity though the promotion of physical activity in the form of walking, cycling and active play [ 26 ]. A reduction in background noise may also allow urban populations to hear wildlife more clearly, however the potential benefits of reducing speed limits on wellbeing amongst residents has not routinely been researched.

In this study, we aimed to test whether listening to natural soundscapes can aid stress recovery and reduce anxiety in student participants exposed to noise pollution and whether reducing traffic speeds affects psychological responses to these natural sounds. Specifically, we aimed to use two widely applied subjective scales commonly used to measure human mood to test to what extent self-reported anxiety, stress and pleasure are affected by i) natural soundscapes and ii) mixed natural and anthropogenic soundscapes, with the addition of traffic noise recorded on roads with two common speed limits in the UK, 20 mi/h and 40 mi/h (e.g. similar to 30 and 60 km/h). We also tested whether general mood state, age, gender and inherent preference for natural environments affected mood recovery in response to natural and mixed natural and anthropogenic soundscapes.

Participants

Participants (n = 68) were recruited from the University of the West of England (UWE) Psychology participant pool, online on the UWE student’s union survey page and via email between 5 th March-14 th April 2021. Written informed consent was obtained from all participants prior to their participation and they were given the option to withdrawn from the experiment at any time. Psychology students that participated received an incentive of one course credit, but other students were not incentivised. All students that took part were either science, psychology or social science students. We excluded participants that had been diagnosed with or currently taking prescribed medication for psychiatric conditions such as anxiety and depression, as low mood and medication could influence subjective responses. We also wanted to avoid inducing increased stress response in those already suffering from anxiety and depression. Ethical approval was obtained from the university ethics committee prior to the experiment commencing (University of the West of England approval code: HAS.20.11.036).

Soundscapes

We created three 3-minute soundscape files for use in playback experiments using Audacity (v.2.4.2, Audacity Team, open-source software, https://www.audacityteam.org/ ). All three soundscapes included a base of a natural soundscape recording, made at sunrise in West Sussex, UK using a parabolic reflector microphone system (Talinga, Tobo, Sweden). The natural soundscape included a range of common UK bird species likely to be heard in a typical dawn chorus including those recorded on the RSPB’s top 25 Big Garden Birdwatch [ 27 ] and some rarer species such as the nightingale ( Luscinia megarhynchos ). We added anthropogenic soundscapes including traffic noise to the natural soundscape to create the other two mixed natural and anthropogenic soundscapes. Anthropogenic soundscapes including road traffic sounds were recorded on two roads (20 mi/h and 40 mi/h limits) in Bath, UK on the same morning at peak ‘rush hour’ between 8.30–9.00 am, using a Zoom H5 portable recorder (Zoom Inc. Tokyo, Japan) at 1 meter from each road. Traffic volume was consistently high between the two roads and contained rush hour traffic of mainly cars and buses. Soundscapes used in playback experiments therefore included i) a natural soundscape (‘natural’), ii) a mixed natural + anthropogenic soundscape with 20 mi/h traffic (‘mixed 20’) and iii) a mixed natural + anthropogenic soundscape with 40 mi/h traffic (‘mixed 40’).

Experimental design

Data were collected using a bespoke survey designed and administered online using Qualtrics XM software (Qualtrics International, Seattle, United States). Participants were given a basic background and information about the experiment, including that it contained a task to listen to soundscapes and watch videos, but not given any information about the hypotheses (see S1 Doc for exemplar experiment procedure). Participants took part in the experiment in one sitting online for 30 minutes to 1 hour (depending on the time taken to answer questions) ( Fig 1 ). Each participant was exposed to three rounds of a stressor video for 1 minute and soundscape play back of 3 minutes and answered questions after each stressor and each soundscape (12 minutes of exposure to stressors and soundscape in total). At the end of the playback experiment, participants were asked demographics questions (age, gender, ethnicity) and some other questions to gain an understanding of any participant bias (see Demographics and other participant information ).

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The experiment contained 3 sections, each with a stressor video and soundscape recording playback followed by questions measuring subjective current mood. Playbacks were either a natural soundscape (‘Natural’) or a mixed natural and anthropogenic soundscape, with either 20 mi/h (‘Mixed 20’) or 40 mi/h (‘Mixed 40’) traffic sounds added. Sections marked with a * were randomly rotated between the experiment sections for each participant, but stressor video order remained the same.

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Participants were asked to use noise cancelling (over the ear) headphones if available, or ear buds (in the ear) or laptop/computer speakers if they did not have access to headphones. Before starting the experiment, participants were asked about their mood in general (see Subjective Measures below), and then asked to do a sound test. During the sound test, participants were asked to put on their headphones, and click a test link that played some sounds of human talking. They were then asked to adjust their headphones to a level that was comfortable, but loud enough to immerse themselves in the sounds. Talking was chosen as the test sound as it was sufficiently different from the sounds used in the main experiment.

The experiment was comprised of three sections ( Fig 1 ). In each section, each participant was exposed to a stressor video and then asked to rate their current mood (see Subjective Measures below). Participants were then exposed to one of the three soundscapes and again asked to rate their mood, allowing a measure of mood recovery. All participants were played all three stressor videos and all three soundscapes. The order of soundscapes was randomised between participants, but the stressor videos were not ( Fig 1 ). Soundscapes were randomised to control for any order effects, with each participant exposed to all three soundscapes as part of the repeated measures design.

Stressors are often used in psychological research as a way of standardising mood state, before subjecting a participant to a condition [ 11 , 15 ], which in this case was a soundscape playback. We created three multi-modal cognitive stressors including arithmetic, based on methods of similar studies [ 11 , 15 ]. All stressors were 1-minute long video comprised of a written maths question, which was obscured by flashing between different colours of text and background, along with stressful sounds (e.g. either a squeaky noise, annoying music or an alarm beeping). Each video contained a different maths question, sound, and colour pallet. Stressor order was the same for each participant, due to constraints within the survey program design architecture, but we included stressor as a fixed effect in statistical analysis to control for any effect on subjective measures (see Statistical Analysis below).

Subjective measures

In order assess participants mood before and during the experiment, we used two measures commonly used in psychological research and clinical settings to diagnose anxiety and measure acute shifts in mood. Two measures were used to ensure internal consistency in the experiment (i.e. if scores from the two measures mirrored each other, then they were both more likely a true representation of mood). We measured a participant’s general mood as subjective ‘trait’ anxiety (STAI-T) before the experiment, using a validated short form of the State-Trait Anxiety Inventory (STAI) scale ( S1 Fig ) [ 28 , 29 ]. We also measured a participant’s subjective mood changes (i.e. their current mood ‘state’) during the experiment, including after each of the three stressor videos and after each soundscape playback. We measured subjective mood as current ‘state’ anxiety, stress, and pleasure (hedonic tone). State anxiety is defined as a temporarily anxious emotional state influenced by the current situation, hedonic tone is a measure of pleasure in response to a situation, and subjective stress, the level of stress or tension currently felt. We measured current mood in terms of subjective stress and hedonic tone using a short form of the University of Wales Institute of Science and Technology Mood Adjective Checklist (UWIST MACL) [ 30 ]. Participants were asked to rate how they felt currently in terms of four mood items (relaxed, nervous, happy, sad) on a 4-point Likert scale ( S2 Fig ). Current stress was scored as nervous plus reverse relaxed scores and hedonic tone as happy plus reverse sad scores. Therefore, increased subjective stress and increased pleasure (hedonic tone) were represented by higher scores.

We also measured current mood in terms of anxiety (STAI-S) using a validated short form of the STAI scale ( S3 Fig ) [ 28 , 29 ]. Both STAI-S and STAI-T scales included three anxiety present and three anxiety absent items, rated on a 4-point Likert scale ( S1 and S3 Figs). Both STAI-S and STAI-T scores were calculated as the sum of anxiety present items and reverse anxiety absent items scores, so that higher scores represented increased current and general anxiety.

Demographics and other participant information

Self-selected student participants are often used in studies of this type [ 15 , 31 , 32 ] However, despite students being generally regarded as appropriate subjects for this type of study [ 33 ], we wanted to understand any inherent biases that existed in the participant pool. We therefore collected a range of participant information before the main playback experiment to gain an understanding of the biases that may exists in our sample. We then chose a subset of that participant information for use in analysis (see Statistical Analysis ), chosen as they were the most likely to influence a person to being more or less sensitive to natural soundscapes, which could in turn bias the results. We collected demographic data (age, ethnicity, gender), all commonly measured in similar studies examining wellbeing in response to soundscape playbacks (e.g. [ 10 , 13 ]). We also included several questions related to participants’ relationship with their environment. We asked whether participants live, work and grew up in urban, semi-rural or rural environments and whether they had a preference for natural or urban environments (scale: none, slight, strong preference for either urban/rural), whether participants noticed sounds in their environment (4-point scale: not sure, sometimes, often, very often). We also included the type of listening device used to take part in the experiment (in ear or over ear headphones or speakers), as this might influence the ability of the participant to fully engage in the experiment. As bird sound was prominent in all three soundscapes, to rule out any effect of bird phobia, we also included a question asking about phobias in general and included birds in a list of other common phobias (e.g. bats, spiders).

Statistical analysis

We analysed all data using the R package lme4 (v.1.1–26 [ 34 ]) in R Studio (R version 4.0.5) using generalized linear mixed models (GLMMs). We analysed three subjective mood measures datasets, collected as part of the main soundscape playback experiment. Subjective mood measures included stress and hedonic tone (UWIST MACL) and anxiety (STAI-S). We included participant information data included in the analysis a general (trait) anxiety measure ( STAI-T ), demographic variables ( age , gender ), inherent preferences for nature scores ( preference for natural environments ).

Analysis of subjective mood measures

Response variables included stress , hedonic tone and anxiety scores calculated from scores recorded after each soundscape. Fixed effects included in the full model were soundscape (factor variable with levels: ‘natural’, ‘mixed 20’, ‘mixed 40’), STAI-T (continuous variable), age (continuous variables), gender (factor coded as binary: 1 = male, 0 = female, NA = non-binary), preference for natural environments (factor coded as a binary score: 1 = slight and strong preference for natural environments, 0 = slight and strong preference for urban environments or no preference). Each participant was exposed to all stressors and all soundscapes. However, soundscape order was randomised within the Qualtrics software, whereas stressor order was not. We therefore included stressor identifier (factor variable with levels: A, B, C) as a fixed effect in the full model to control for any effect of stressor type or order on the outcome measures. We also chose to use mixed effect models due to their ability to include random effects (as well as fixed effects) and included the random effect of participant number. Using this mixed modelling method allowed us to control for order of the fixed factor effects soundscape and stressor as well as any inherent variation in stress, hedonic tone and anxiety amongst participants.

Modelling procedure

Final models were selected using a backwards step-wise model selection procedure to find the most parsimonious yet best fitting model. Fixed effect variable terms were removed sequentially, and likelihood ratio tests (LRTs) (ANOVA) were performed between models with and without that term. Variables that were significant in LRTs were retained in the final model and non-significant terms were removed. Models were also compared based on their second order Akaike Information Criterion (AICc) and the model with the lowest AICc that contained all significant terms was chosen as the final model. Relevant interaction effects were also tested in the same way. Tukey contrast tests were also performed on final models to test for differences between soundscape levels. Statistics are presented in tables, including model summary statistics (estimates and s.d. for fixed effects and variance and s.d for random effects), likelihood ratio tests (χ 2 , d.f. and p value) and Tukey contrast statistics (estimate, SE, z and p values). We tested whether residuals were normal for LMMs and validated all models using a simulation method in the Dharma package in R [ 35 ], which tested for homogeneity of variance, zero inflation and overdispersion (v0.4.5).

Participant information and demographics

Participants (n = 68) were mainly white British female undergraduate in their first- or second year studying science and psychology/social science students, living and working in an urban environment ( S1 Table ). Participants had an age range of 18–42. Most participants (66.18%) either had a slight or strong preference for natural environments and 22.06% and 38.24% reported noticing sounds sometimes and very often in their environment. Most participants grew up in semi-rural (39.71%) or urban (44.12%) environments. Only 1.4% of participants had a bird phobia. Most participants used headphones (in ear 41.18%, over ear 36.76%) to listen to the soundscapes and 22% listened on laptop speakers.

Current stress and anxiety were lower and pleasure (hedonic tone) scores higher in participants after experiencing all three soundscapes when compared to the three stressors ( Table 1 , Fig 2 ). There was a significant effect of soundscape treatment on all three subjective measures ( Table 2 , see S3 Table for model selection statistics). Current stress and anxiety scores increased across soundscape treatments ( Fig 2 ; S2 Table ). We recorded significant differences between the ‘natural’ and ‘mixed 40’ treatments for current stress (UWIST MACL) and ‘natural’ vs ‘mixed 20’ and ‘natural’ vs ‘mixed 40’ treatments for current anxiety (STAI-S) ( Table 3 ). Pleasure scores (hedonic tone) were lower after exposure to the ‘mixed 40’ when compared to both ‘natural’ and ‘mixed 20’, however this was marginally non-significant when analysed with post-hoc Tukey contrasts ( Table 3 ), despite soundscape treatment being a significant fixed effect when analysed with a GLMM ( S2 Table ).

Stress (UWIST MACL) was scored as nervous plus reverse relaxed scores and hedonic tone as happy plus reverse sad scores. Therefore, increased subjective stress and increased (positive) hedonic tone were represented by higher scores. Anxiety scores were calculated from the STAI-S scale as the sum of anxiety present items and reverse anxiety absent items scores, so that higher scores represented increased anxiety. Significance stars are presented for Tukey contrasts (. = p < 0 . 1 , * = p < 0.05, ** = p < 0.01, *** = p < 0.001).

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There was a significant positive trend between general ‘trait’ anxiety (STAI-T) and current stress (UWIST MACL) and anxiety (STAI-S) scores ( Fig 3 ). However, pleasure (hedonic tone) decreased with increased general ‘trait’ anxiety (STAI-T) scores ( Fig 3 ). General ‘trait’ anxiety (STAI-T) score was also significant when included as a fixed effect in GLMMs for all three measures (Tables 2 and S2 ).

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Stressor had no effect on current stress (UWIST MACL) or anxiety STAI-S scores, but pleasure (hedonic tone) scores were significantly different between stressors and so this variable was controlled for and retained in the final model for hedonic tone ( S2 Table ).

This online study set out to assess the effect on participants mood of listening to a natural soundscape including birdsong, following exposure to a multi-modal cognitive stressor, and whether the addition of anthropogenic soundscapes including road traffic of different speeds also affected mood recovery. We show that listening to a natural soundscape (including bird song) can reduce self-reported current stress and anxiety levels, and that mood recovery (after a stressor) is lessened on addition of road traffic soundscapes. Positive mood (pleasure/hedonic tone) was also enhanced by the natural soundscape, but this was limited by traffic sounds. Results indicated that the natural soundscape alone was associated with the lowest levels of self-reported current anxiety and stress levels which then increased on listening to the mixed soundscape with 20 mi/hr road traffic, with the highest levels reported after the mixed soundscape with 40mi/h road traffic. Higher levels of pleasure (hedonic tone), reflecting positive mood, were reported after listening to the natural soundscape, but reduced in comparison after listening to the mixed natural and 40mi/h traffic soundscape.

Do natural soundscapes improve mood?

When participants were exposed to the natural soundscape they had the lowest levels of subjective stress and anxiety relative to soundscapes including anthropogenic noise. This supports previous findings highlighting the positive impact that natural soundscapes can have on stress recovery and mental fatigue [ 8 , 14 , 36 , 37 ]. Our result therefore highlights the importance of the retention of suitable sized urban greenspace that are accessible to the public and large enough to support wildlife populations beyond the reach of anthropogenic pollutants such as traffic noise. This supports [ 38 ] who call for the urban populace to experience more robust, healthy and even wilder forms of nature, away from human disturbances. Access to greenspace rapidly reduces as cities grow, which reduces opportunities for people to experience nature [ 39 ], it is therefore essential that future urban development and expansion occurs with the provision of greenspace included to maximise the health and wellbeing benefits from these spaces.

What are the benefits of reducing traffic speeds on mood?

Anthropogenic noise reduces the human ability to hear natural sounds, for example the ability of ornithologists to detect birds (e.g. [ 40 ]). Our results show that the presence of traffic noise does mask the positive impact of a natural soundscape on stress and anxiety in participants and that this was irrespective of age, gender or a pre-disposed preference for natural environments. We found a trend of decreasing stress and anxiety scores, with a decrease in traffic speed across the conditions, despite not all treatment comparisons being significant during multiple comparison tests. For example, there was no significant difference in levels of subjective stress between hearing a natural soundscape and natural soundscape alongside 20mi/h road noise, in contrast to 40mi/h traffic where both stress and anxiety were heightened. Pleasure was also reduced during the higher traffic speed condition, but we recorded no difference between the natural soundscape and the mixed 20mi/hr traffic condition and only small differences recorded in the other treatment comparisons. The reason for these results is likely the differing sensitivity of the two subjective measures in their ability to pick up the differences in mood caused by the treatments, which is why we chose to include two measures (e.g. UWIST MACL has less mood items to score than the STAI-state measure, which may make it comparatively more sensitive) ( S1 – S3 Figs). Despite some between treatment comparisons being non-significant, soundscape was a significant predictor of all three mood item scores and the trend was for higher traffic speeds to reduce mood recovery in comparison to when natural soundscapes were heard alone. Reduced traffic speeds can therefore be a positive intervention in improving accessibility to nature as well as reducing road injuries [ 41 ] and encouraging active play [ 26 ].

How can reducing traffic speed influence health and wellbeing?

Anthropogenic noise pollution is associated with hypertension, cardiovascular disease risk [ 19 , 20 ], and an increased risk of mental health conditions, including depression and anxiety symptoms [ 21 – 23 ]. Our results show that for those with high baseline anxiety levels (so-called ‘trait’ anxiety STAI-T), exposure to anthropogenic soundscapes will lead to heightened levels of anxiety and stress, highlighting the pressures that many people will be exposed to on city streets on a daily basis. Trait anxiety (STAI-T) is a relatively stable characteristic reflecting the general background levels of anxiety experienced by individuals and is likely to be associated with other personality characteristics as well as mood states. Our results show that those participants with higher trait anxiety levels also reported higher current ‘state’ anxiety–how anxious they felt at the point of assessment, and similarly higher stress scores when compared to those with lower levels of trait anxiety who reported correspondingly lower state anxiety and stress. In addition, a significant proportion of people suffering from clinical levels of depression will also have anxiety [ 42 ]. A recent review of the mechanisms of anthropogenic noise impacts on mental health has pointed to a direct impact on the central nervous system, including adverse changes in brain tissue when people are exposed to traffic noise in their immediate environment every day [ 23 ]. Our study shows that exposure to natural soundscapes may alleviate some of the adverse effects on health and wellbeing caused by anthropogenic noise pollution. Therefore, the inclusion of wildlife and associated green environments within urban areas where over 80% of the UK population lives [ 43 ] may then benefit those suffering from these conditions, and possibly help prevent the transition of negative mood to a clinical level requiring treatment.

Study limitations, research directions and recommendations

Like other studies of this kind, we used a student participant pool [ 15 , 31 , 32 ]. Although there is president for doing so among the literature [ 33 ], participants may have been predisposed to favour natural soundscapes, due to their age, sex or backgrounds. However, neither age, sex nor preference for the natural environment influenced mood response to the soundscapes, despite inherent biases existing in the participant pool. This study included playbacks including a number of different bird sounds making up a dawn chorus soundscape but did not change the level of biodiversity represented in the soundscape. Future studies could therefore include participants from a range of backgrounds and ages, with both sexes represented equally, to examine how participant socio-cultural background may influence responses to different elements of soundscapes, and whether prior knowledge of bird song influences response. Understanding how biodiversity impacts wellbeing via the sonic environment is an important avenue for future research, including the question of whether more biodiverse soundscapes are better at enhancing mood recovery. It is also important to understand the interaction between anthropogenic sounds and biodiversity in the sonic environment in relation to urban planning and effects on human health and wellbeing. From our study, it is clear that a reduction in urban speed limits would have benefits to human wellbeing in urban environments. Further research is also needed to understand how technological adaptations to the urban soundscape, such as the widespread transition to hybrid and electric vehicles, could reduce the impact of noise pollution on both human and wildlife in cityscapes. We recommend work that explores the redesign of major urban transit routes, both for potentially polluting motor vehicles and for pedestrian walkways or cycle paths, to include green spaces and significant vegetation that encourages wildlife. Greening in this way will in turn will dampen traffic noise, help absorb air born pollutants as well as benefitting mental health supporting a healthier travelling public [ 3 , 5 , 44 ].

There is increasing pressure to implement reduced speed limits within cities, however speed reduction initiatives are still met with considerable resistance amongst policymakers and local communities. Here, we demonstrate that a reduction in traffic speed and therefore noise pollution can aid stress recovery and reduce anxiety highlighting the importance of exposing urban populations to wildlife. The reduced level of stress, anxiety and higher level of pleasure (hedonic tone) experienced by participants when exposed to a natural soundscape compared to a stressor event, even in the presence of masking anthropogenic sounds, highlight the importance of being able to hear natural sounds in our cities. City-wide strategies such as reducing road traffic speeds and conserving urban greenspace are therefore necessary steps to aid stress recovery and reduce anxiety.

Supporting information

S1 doc. survey example experienced by participants..

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S1 Fig. Example of scale presented to participants to rate their general mood (trait anxiety).

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S2 Fig. Example of scale presented to participants to rate their current mood in terms of stress and hedonic tone (pleasure).

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S3 Fig. Example of 4-point Likert scale presented to participants after each stressor video and soundscape file.

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S1 Table. Demographic data for all participants.

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S2 Table. GLMM statistics for subjective measures UWIST MACL stress and hedonic tone (pleasure) and STAI-S current state anxiety scores.

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S3 Table. Model selection statistics for GLMM for three subjective measures, UWIST MACL stress and hedtone and STAI state anxiety.

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S1 Data. Current state anxiety (STAI-S) dataset.

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S2 Data. UWIST MACL dataset (stress and hedonic tone).

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Acknowledgments

We would like to thank Gary Moore for the use of his bird song soundscape and for recording traffic noise for us.

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