Noise Pollution

Noise and human hearing

Who is affected?

The federal government and noise

Protection from noise

Resources

As late as the 1950s, most of the sounds on the planet Earth were probably still of natural origin rather than derived from technological sources. Today, however, the opposite appears to be true. Noise pollution, sometimes called environmental pollution, is human or machine sounds that are created, which disrupt the natural environment and society in general.

Cars, trucks, lawn mowers, leaf blowers, chain saws, power drills, television, radio, video games, computers, and so forth adds to an almost endless list of noise makers in modern life. Moreover, the world keeps getting noisier. Noise—which can be defined as unwanted sound waves that were not present in the pre–modern electromagnetic spectrum—is one of the most common forms of pollution, one that can easily damage the hearing and general health of people and animals.

Noise and human hearing

The inner ear of humans (and other vertebrates) contains a snail–shaped structure called a cochlea that is lined with thousands of microscopic hairs. When sound vibrations enter the cochlea, they cause the tiny hairs to move back and forth. If strong vibrations blast into the cochlea, the hairs can be flattened and damaged. The damage usually results in some degree of hearing loss.

Sound is measured in decibels (dB). Zero dB represents the quietest sound that a healthy human can hear. One hundred dB equals a noise that is 10 billion times as intense as one dB. Brief exposure to more than 110 dB can damage ears immediately; prolonged exposure to more than 85 dB can damage ears gradually.

Examples of decibel–level sounds that one may encounter in modern life are as follows:

• Quiet library or soft whisper—30 dB,
• Normal conversation—50 to 60 dB,
• Busy traffic or noisy restaurant—70 dB,
• Subways, heavy city traffic, alarm clock at 2 ft (61 cm), or factory noise—80 dB,
• Noise in industrial plants, or call centers—90 dB,
• Train traveling 45 mi (28 km) per hour—93 dB,
• Chain saw, stereo headphones, night club or pneumatic drill—100 dB,
• Loudest sound that can be tolerated by the human ear—about 120 dB,
• Sound at a rock concert in front of speakers, sandblasting, or thunderclap—120 dB,
• Gunshot blast or jet plane—140 dB,
• Automobile drag race—171 dB, and
• Sound at a rocket launching pad—180 dB.

As noted, the most powerful sounds that humans encounter include jets taking off, loud amplified music, gun shots, and chain saws. Just a single exposure to these sounds can damage human ears.

Humans also damage ears if they are exposed to noises that are less loud, but that are heard more often. For example, office workers who daily endure noise from telephones and loud machines may suffer some hearing loss over time. Workers in loud factories also experience hearing loss.

People can even hurt their hearing when playing. Motorboats, motorcycles, and snowmobiles all make loud noises likely to hurt ears. Playing loud music on a personal stereo can also damage hearing. If someone near can hear the music someone else is playing on their personal stereo, then that person is probably causing noise pollution for others and hearing loss for themselves.

Noise hurts more than just hearing. When people are exposed to loud noise, bodies react as if in danger. Physiological responses to noise include increased heart rate, stress, eye conditions, muscle tension, elevated cholesterol levels and hormone secretion, and of course high blood pressure; even migraines can be induced by noise. Noise also impairs concentration. Studies have shown that children’s learning and achievement can be also be affected by exposure to noise. Noise over 55 decibels can disrupt sleep and produce aggression if it is uninvited and persists long enough. While such a situation might be acceptable for a short time, millions of people around the world live with excessive noise every day and night.

A noise level of 75 decibels generates high levels of stress in most people. Tinnitus, or ringing in the ear, may occur at 80 decibels. The 100 decibels regularly encountered in nightclubs can cause ear damage after only fifteen minutes. Noise can also induce mental states that lead to suicide and homicide. In Great Britain, anti–noise campaigners are keeping a count of the number of crime–related deaths that occur each year traceable to a response to noise.

Who is affected?

Over ten million Americans today have lost part of their hearing because of noisy lives. People who work at airports seem especially at risk: One study suggests that more than half the people working near runways suffer some hearing loss. Noise pollution tends to be just as much a problem in other countries as in the United States. For example, one scientist studied people who worked in a paper mill in India. Noise levels ranged between 80 to 100 dB all day. More than one–third of the workers showed some hearing loss. In Germany, citizens and companies spend nearly four billion dollars a year correcting hearing problems.

Noise pollution can also cause distress in life forms other than human. For example, sudden loud noises can wake hibernating animals. This, in turn, raises their metabolic rates and can cause them to consume fat reserves they need to survive through to spring.

Sounds produced by humans can also interfere with the ability of animals to communicate. Such interference can inhibit an animal’s ability to protect itself, to find food, and to live a normal life. For example, ships emit low–frequency sounds that interfere with whale communications. Other human noises can frighten whales away from their normal migration routes. In the desert, kangaroo rats (Dipodomys spp.) exposed to the roar of a dune buggy lose their ability to hear snakes approaching. Japanese quail (Coturnix Coturnix Japonica ) have to call much louder than usual when they live in a noisy environment. Sooty terns (Sterna fuscata ) have been observed to abandon their nests when jets create sonic booms. Intense bursts of noise have also caused condors (Gymnogyps californianus ) to abandon their nests.

The federal government and noise

Because noise pollution causes so many problems, the U.S. government has passed laws to regulate noise. In 1987, for example, Congress passed the National Overflights Act. This law called for studies to determine the effect of air traffic over national parks. It also prohibited low–flying planes from flying over certain parts of Grand Canyon National Park.

Since 1972, when the Noise Control Act (formally, the Noise Pollution and Abatement Act of 1972) was passed, the Environmental Protection Agency (EPA) has been responsible for researching and regulating noise pollution in the United States. The Noise Control Act reads in part as follows: “The Congress declares that it is the policy of the United States to promote an environment for all Americans free from noise that jeopardizes their health or welfare.” Between 1972 and 1981, EPA’s Office of Noise Abatement and Control (ONAC) issued hundreds of reports about the severity of noise pollution in the United States, trained community leaders in ways to reduce noise pollution, and recommended numerous regulations to reduce the impact. Its work was designed to educate communities and set uniform emission standards throughout the country. In 1982, however, ONAC was shut down as part of President Ronald Reagan’s deficit reduction plan. The Noise Control Act was never repealed or amended, but it was no longer enforced at the federal level. By 1999, the poorly funded ONAC was maintaining only a skeleton office. At the same time, some sections of the Noise Control Act pertaining to labeling, noise emission standards, and noise sources were in need of updating.

As of 2006, noise pollution is viewed as an environmental problem in the United States and many other industrialized countries. Federal, state, and local laws and standards have been enacted to minimize noise. Road development and urban planning must take into consideration the noise that they will generate during the construction and maintenance of such projects. Building codes specifically state restrictions to noise. The Noise Control Act has been discontinued at the federal level. However, it has been taken up at the state and municipal levels, especially concerning transportation noise. Many cities in the United States, especially those in California, are passing laws and regulations that establish guidance to minimize noises in the public domain. Allowable sound levels are regularly enforced through noise ordinances throughout cities across the United States.

Protection from noise

Individuals can take many simple steps to protect themselves from the harmful effects of noise pollution. If people must be around loud sounds, they can protect their ears with earplugs or ear protectors. They can muffle sound by using acoustic ceiling tiles, draperies, carpets, and sound–absorbing furniture in their homes, offices, and schools. They can also buy quieter models of machines and let storeowners and manufacturers know that they prefer quieter products. Individuals can also help their communities investigate noise pollution and develop regulations to reduce the problem locally.

Some communities have enacted anti–noise ordinances. New York City issues fines to people who run excessively noisy air conditioners, to street construction crews whose equipment is too loud, and to impatient drivers who honk their horns. Police in Redondo Beach, California, can remove large speakers from cars if the music can be heard more than 50 ft (15.2 m) away.

Communities can also reduce noise by locating freeways far from residential neighborhoods, by reducing the speed on freeways and other high–speed roads, by requiring developers to plant trees and shrubbery as sound mufflers, and by requiring people to build houses and other structures with materials that help absorb sound.

Many engineers are aware of the need to reduce noise pollution, and some of them are busy devising new ways to solve the noise problem. In Japan, Yokohama Tire Company has introduced a new high–performance tire that gives a quieter ride. Korean engineers have developed an anti–noise system for computers that reduces a typical noise level of 30 decibels to a nearly undetectable 20 decibels. U.S. researchers have invented a new composite consisting of alternating layers of sound–absorbing foam and sound–containing vinyl that can be placed in machinery housings to reduce noise. At the Georgia Institute of Technology, an inventor has developed a quiet curtain for nursing home patients who cannot sleep that is made of noise–absorbing materials that can reduce noise by 12 decibels. In Germany, roads are paved with materials that reduce sound, tires are manufactured to whine less, and lawn mowers and other equipment are designed to operate quietly. Manufacturers in some Australian states must label the noise level of products such as chain saws and lawn mowers.

As the human population continues to increase, the amount of noise in the world will also grow as people crowd together with gadgets, machines, and vehicles. To help ease the impact of this increasing amount of noise, some companies are developing a new technology called anti–noise (similar to white noise). Anti–noise works by emitting a sound that exactly matches the noise. When the sound waves from the anti–noise device meet the sound waves from the noise, they cancel each other out. In such a case, no sound waves reach our ears; humans do not hear the noise. Anti–noise can work as a kind of muffler on a noisy engine, or it can be built into headphones to silence all approaching noise. Even if humans cannot eliminate noise pollution, it may be possible to use anti–noise devices to escape some of the damage that noise can cause.

KEY TERMS

Anti–noise —Sound wave produced by a computer that matches the sound wave of an offending sound; when the two sound waves meet, the anti–noise cancels out the noise.

Cochlea —A snail–shaped structure in the inner ear which contains the anatomical structures responsible for hearing.

Decibel —A unit of measurement of the intensity of sound, abbreviated dB.

Noise —Any unwanted, annoying, or disturbing sound; especially sound that can cause physical or psychological damage.

Resources

BOOKS

Hansen, Colin H. Noise Control: From Concept to Application. London, UK, and New York: Taylor & Francis, 2005.

Hansen, Colin H. Understanding Active Noise Cancellation. London, UK, and New York: Spon Press, 2001.

Moser, Michael. Engineering Acoustics: An Introduction to Noise Control. Berlin, Germany, and New York: Springer, 2004.

Wang, Lawrence K., Norman C. Pereira, and Yung–Tse Hung, eds. Advanced Air and Noise Pollution Control. Totowa, NJ: Humana Press, 2005.

Carolyn Duckworth

Randall Frost

Noise pollution

As late as the 1950s, most of the sounds on this planet were probably still of natural origin rather than derived from technological sources. Today, however, the opposite appears to be true.

Cars, trucks, lawn mowers, leaf blowers, chain saws, power drills, television , radio , video games, computers... the list of noise makers in our modern life is almost endless, and our world keeps getting noisier. Noise—which can be defined as unwanted sound waves that were not present in the pre-modern electromagnetic spectrum—is one of the most common forms of pollution , one that can easily damage the hearing and general health of people and animals.

Noise and our hearing

The inner ear of humans (and other vertebrates ) contains a snail-shaped structure called a cochlea that is lined with thousands of microscopic hairs. When sound vibrations enter the cochlea, they cause the tiny hairs to move back and forth. If strong vibrations blast into the cochlea, the hairs can be flattened and damaged. The damage usually results in some degree of hearing loss.

Sound is measured in decibels (dB). Zero dB represents the quietest sound that a healthy human can hear. One hundred dB equals a noise that is 10 billion times as intense as one dB. Brief exposure to more than 110 dB can damage ears immediately; prolonged exposure to more than 85 dB can damage ears gradually.

Examples of decibel-level sounds that one may encounter in modern life are as follows:

• quiet library or soft whisper—30 dB
• normal conversation—50-60 dB
• busy traffic or noisy restaurant—70 dB
• subways, heavy city traffic, alarm clock at 2 ft (61 cm), or factory noise—80 dB
• noise in industrial plants, or call centers—90 dB
• train traveling 45 mi (28 km) per hour—93 dB
• chain saw, stereo headphones, night club or pneumatic drill—100 dB
• loudest sound that can be tolerated by the human ear—about 120 dB
• sound at a rock concert in front of speakers, sandblasting, or thunderclap—120 dB
• gunshot blast or jet plane—140 dB
• automobile drag race—171 dB
• sound at a rocket launching pad—180 dB

As noted, the most powerful sounds we encounter include jets taking off, loud amplified music, gun shots, and chain saws. Just a single exposure to these sounds can damage our ears.

We also damage our ears if we are exposed to noises that are less loud, but that are heard more often. For example, office workers who daily endure noise from telephones and loud machines may suffer some hearing loss over time. Workers in loud factories also experience hearing loss.

We can even hurt our hearing when we play. Motorboats, motorcycles, and snowmobiles all make loud noises likely to hurt our ears. Playing loud music on a personal stereo can also damage hearing. If someone near you can hear the music you are playing on your personal stereo, you are probably causing noise pollution for them and hearing loss for yourself.

Noise hurts more than our hearing. When we are exposed to loud noise, our bodies react as if we were in danger. Physiological responses to noise include increased heart rate, stress , eye conditions, muscle tension, elevated cholesterol levels and hormone secretion, and of course high blood pressure; even migraines can be induced by noise. Noise also impairs concentration . Studies have shown that children's learning and achievement can be also be affected by exposure to noise. Noise over 55 decibels can disrupt sleep and produce aggression if it is uninvited and persists long enough. While such a situation might be acceptable for a short time, millions of people around the world live with excessive noise every day and night.

A noise level of 75 decibels generates high levels of stress in most people. Tinnitus, or ringing in the ear, may occur at 80 decibels. The 100 decibels regularly encountered in night clubs can cause ear damage after only fifteen minutes. Noise can also induce mental states that lead to suicide and homicide. In Great Britain, anti-noise campaigners are keeping a count of the number of crime-related deaths that occur each year traceable to a response to noise.

Who is affected?

As many as 10 million Americans today have lost part of their hearing because of our noisy lives. People who work at airports seem especially at risk: One study suggests that more than half the people working near runways suffer some hearing loss. Noise pollution tends to be just as much a problem in other countries as in the United States. For example, one scientist studied people who worked in a paper mill in India. Noise levels ranged between 80-100 dB all day. More than one-third of the workers showed some hearing loss. In Germany, citizens and companies spend nearly four billion dollars a year correcting hearing problems.

Noise pollution can also cause distress in life forms other than human. For example, sudden loud noises can wake hibernating animals. This, in turn, raises their metabolic rates and can cause them to consume fat reserves they need to survive through to spring.

Sounds produced by humans can also interfere with the ability of animals to communicate. Such interference can inhibit an animal's ability to protect itself, to find food, and to live a normal life. For example, ships emit low-frequency sounds that interfere with whale communications. Other human noises can frighten whales away from their normal migration routes. In the desert , kangaroo rats (Dipodomys spp.) exposed to the roar of a dune buggy lose their ability to hear snakes approaching. Japanese quail (Coturnix Coturnix Japonica) have to call much louder than usual when they live in a noisy environment. Sooty terns (Sterna fuscata) have been observed to abandon their nests when jets create sonic booms. Intense bursts of noise have also caused condors (Gymnogyps californianus) to abandon their nests.

The federal government and noise

Because noise pollution causes so many problems, the United States government has passed laws to regulate noise. In 1987, for example, Congress passed the National Overflights Act. This law called for studies to determine the effect of air traffic over national parks. It also prohibited low-flying planes from flying over certain parts of Grand Canyon National Park.

Since 1972, when the Noise Control Act was passed, the Environmental Protection Agency (EPA) has been responsible for researching and regulating noise pollution in the United States. The Noise Control Act reads in part as follows: "The Congress declares that it is the policy of the United States to promote an environment for all Americans free from noise that jeopardizes their health or welfare." Between 1972 and 1981, EPA's Office of Noise Abatement and Control (ONAC) issued hundreds of reports about the severity of noise pollution in America, trained community leaders in ways to reduce noise pollution, and recommended numerous regulations to reduce the impact. Its work was designed to educate communities and set uniform emission standards throughout the country. In 1982, however, ONAC was shut down as part of President Reagan's deficit reduction plan. The Noise Control Act was never repealed or amended, but it was no longer enforced at the federal level. By 1999, the poorly funded ONAC was maintaining only a "skeleton" office. At the same time, some sections of the Noise Control Act pertaining to labeling, noise emission standards, and noise sources were in need of updating.

Protection from noise

Individuals can take many simple steps to protect themselves from the harmful effects of noise pollution. If people must be around loud sounds, they can protect their ears with ear plugs or ear protectors. They can muffle sound by using acoustic ceiling tiles, draperies, carpets, and sound-absorbing furniture in their homes, offices, and schools. They can also buy quieter models of machines and let store owners and manufacturers know that they prefer quieter products. Individuals can also help their communities investigate noise pollution and develop regulations to reduce the problem locally.

Some communities have enacted anti-noise ordinances. New York City issues fines to people who run excessively noisy air conditioners, to street construction crews whose equipment is too loud, and to impatient drivers who honk their horns. Police in Redondo Beach, California, can remove large speakers from cars if the music can be heard more than 50 ft (15.2 m) away. In 1999, a judge in Fort Lupton, Colorado, began sentencing teenagers convicted of playing their stereos at high volumes to time spent listening to court-selected vocal artists.

Communities can also reduce noise by locating freeways far from residential neighborhoods, by reducing the speed on freeways and other high-speed roads, by requiring developers to plant trees and shrubbery as sound mufflers, and by requiring people to build houses and other structures with materials that help absorb sound.

Many engineers are aware of the need to reduce noise pollution, and some of them are busy devising new ways to solve the noise problem. In Japan, Yokohama Tire Company has introduced a new high-performance tire that gives a quieter ride. Korean engineers have developed an anti-noise system for computers that reduces a typical noise level of 30 decibels to a nearly undetectable 20. United States researchers have invented a new composite consisting of alternating layers of sound-absorbing foam and sound-containing vinyl that can be placed in machinery housings to reduce noise. At the Georgia Institute of Technology, an inventor has developed a "quiet curtain" for nursing home patients who cannot sleep that is made of noise-absorbing materials that can reduce noise by 12 decibels. In Germany, roads are paved with materials that reduce sound, tires are manufactured to whine less, and lawn mowers and other equipment are designed to operate quietly. Manufacturers in some Australian states must label the noise level of products such as chain saws and lawn mowers.

As the human population continues to increase, the amount of noise in our world will also grow as we crowd together with gadgets, machines, and vehicles. To help ease the impact of this increasing amount of noise, some companies are developing a new technology called anti-noise. Anti-noise works by emitting a sound that exactly matches the noise. When the sound waves from the anti-noise device meet the sound waves from the noise, they cancel each other out. In such a case, no sound waves reach our ears; we do not hear the noise. Anti-noise can work as a kind of muffler on a noisy engine, or it can be built into headphones to silence all approaching noise. Even if we cannot eliminate noise pollution, we may be able to use anti-noise devices to escape some of the damage that noise can cause.

Resources

books

Bragdon, Clifford. Noise Pollution: The Unquiet Crisis. Philadelphia: University of Pennsylvania Press, 1970.

Harris, Cyril. Handbook of Noise Control. New York: McGraw Hill, 1979.

periodicals

Allman, William. "Good News About Noise." U.S. News andWorld Report (September 9, 1991): 59.

Angus, Robert. "Raising a Ruckus About Noise: It Threatens Your Hearing and Your Health." Omni, (February 1994): 18.

Browne, Malcolm. "Human Noises in Ocean Held to Threaten Marine Mammals." New York Times, (October 19, 1993).

Lee, David. "Breaking the Sound Barrier: The Rapidly Growing Air Tour Industry is Generating Unacceptable Noise Levels in Some of Our Most Treasured National Parks." National Parks, (July/August 1994): 24.

LeGro, Bill, and Doug Bruce. "Noise-proof Your Health." Prevention, (January 1993): 50.

O'Brien, Bill. "Quest for Quiet." Sierra, (July/August 1992): 41.

Raloff, Janet. "Dormant Noise Program's Silent Reverberations." Science News, (August 17, 1991): 100.

Shapiro, Sidney. "Rejoining the Battle Against Noise Pollution." Issues in Science and Technology, (Spring 1993): 73.

Sundstrom, Eric, et al. "Office Noise, Satisfaction, and Performance." Environment and Behavior (March 1994): 195.

Toufexis, Anastasia. "Now Hear This—If You Can." Time (August 5, 1991): 50.

Carolyn Duckworth
Randall Frost

KEY TERMS

Anti-noise

—Sound wave produced by a computer that matches the sound wave of an offending sound; when the two sound waves meet, the anti-noise cancels out the noise.

Cochlea

—A snail-shaped structure in the inner ear which contains the anatomical structures responsible for hearing.

Decibel

—A unit of measurement of the intensity of sound, abbreviated dB.

Noise

—Any unwanted, annoying, or disturbing sound; especially sound that can cause physical or psychological damage.

Pollution, Noise

BIBLIOGRAPHY

Noise pollution is undesired sound that is disruptive or dangerous and can cause harm to life, nature, and property. It is often said that noise differs from other forms of pollution in that, unlike atmospheric pollutants for example, once abated, noise leaves no residual accumulation in the environment or the human body. Noise does leave behind its effects, however, and these can deteriorate after continued exposure to harmful sounds. So it is not true, strictly speaking, that “noise … leaves no visible evidence” (Lai 1996, p. 389).

The hazardous effects of noise depend on its intensity (loudness in decibels), duration, and frequency (high or low). High and low pitch is more damaging than middle frequencies, and white noise covering the entire frequency spectrum is less harmful than noise of a specific pitch. Noise may be ambient (constantly present in the background) or peak (shorter, louder sounds).

Noise-induced hearing loss (NIHL) in humans is the major, though by no means only, problem stemming from noise pollution. In 1978 the U.S. Environmental Protection Agency (EPA) Office of Noise Abatement and Control estimated that around twenty million Americans were exposed daily to noise resulting in permanent hearing loss (EPA 1978). In 1990 about thirty million people in the United States were exposed daily to occupational noise levels above 85 decibels, compared with just over 9 million people in 1981. Exposure for more than 8 hours a day to sound in excess of 85 decibels is potentially hazardous. In Germany and other developed countries, as many as four to five million people, that is, 12 to 15 percent of all employed people, are exposed to noise levels of 85 decibels or more (World Health Organization 2001).

Loud, abrupt sounds can harm the eardrum, while sustained sounds at lower volume can damage the middle ear; both types of sounds can cause psychological damage. Noise disrupts sleep and communication, and numerous studies have documented the heart-related, respiratory, neurological, and other physiological effects of noise. Stress, high blood pressure, anger and frustration, lower resistance to disease and infection, circulatory problems, ulcers, asthma, colitis, headaches, gastrointestinal disorders, and many other physiological and psychological problems have been linked directly to noise. In addition, children have been shown to suffer from slower language development and disruption of learning as a result of noise. More than five million children in the United States, ages six to nineteen, suffer from noise-induced hearing impairment (Havas 2006). In the United Kingdom, Netherlands, and Spain, exposure to noise impaired children’s reading comprehension and caused a delay in reading skills development (Clark and Stansfeld 2005). In Austria, children in noisier neighborhoods were shown to suffer from increased stress and diminished motivation (Evans et al. 2001). A fetus exposed to noise may experience a change in heart rate, or it may suffer the impact of its mother’s noise-related stress.

In addition, noise can harm animals and the environment, as well as physical property. Livestock and pets are harmed by noise, as are animals in the wild. Noise can also disturb wildlife feeding and breeding. Noise-related property damage includes structural damage from vibrations induced by sound waves and economic harm in the form of lower property values. The true social costs of noise pollution also must include monetary losses from sickness, absenteeism, loss of productivity and earning capacity, and much more.

Noise pollution is not new, but it has become more problematic with the developments associated with industrialization and urbanization. Between 1987 and 1997, community noise levels in the United States were estimated to have increased by 11 percent and were predicted to continue increasing at that rate or more (Staples 1997). Commercial and industrial activities, construction, aircraft, vehicular traffic (highway and off-road), and the rapid increase in the use of machines and other technologies are all associated with noise pollution. Modern household appliances and lawn and gardening equipment are increasingly common sources of noise. Like many other forms of pollution, noise appears to disproportionately affect poor and disadvantaged minority communities, and so is also an environmental justice issue.

In the United States, public policy to address noise pollution began in the early 1970s. The Noise Control Act of 1972 charged the federal government with protecting public health and welfare from noise pollution by establishing standards for noise emissions and by authorizing federal agencies to establish rules. The EPA created the Office of Noise Abatement and Control (ONAC) as a result of the Noise Control Act. The Quiet Communities Act of 1978 authorized the EPA to provide grants to state and local governments for noise abatement. In the early 1980s the Occupational Safety and Health Administration (OSHA) set standards for industrial noise exposure and criteria for hearing protection. The OSHA guidelines resulted in a reduction of noise levels and hearing loss to workers, but some hearing loss can occur even at OSHA-approved levels. In 1981 Congress agreed to the Ronald Reagan administration’s proposal to cease funding for ONAC, although Congress did not repeal the Noise Control Act when it eliminated ONAC’s funding.

Noise pollution can be controlled through reduction at the source, interruption of transmission paths, or protection of the receiver. Reengineering machines and simply turning down volume when possible are methods of reduction at the source. Barriers, enclosures, and other forms of soundproofing can interrupt transmission paths. The use of hearing protection is the main form of receiver protection. Experts recommend a multifaceted approach, including appropriate training on the use of equipment and on why ear protection matters, enforcement of hearing-protection regulations, and the use of new technologies that reduce noise at the source (Lusk et al. 2004). Like many other environmental problems, addressing noise pollution is complicated by issues of shared responsibility and jurisdiction, making some conventional economic approaches less effective and inviting new interdisciplinary solutions. New active noise control (ANC) technologies may assist in dealing with noise pollution in the years ahead through the use of digital processors that convert analog sounds into digital signals, allowing computer-generated “antinoise” to erase sound with sound (Alper 1991).

While market-based approaches to pollution control have become more popular in recent years, there have not yet been any emissions trading or pollution permits schemes applied to noise. It should be recalled, however, that up until the time of the first government regulation of pollution, a market-based approach was the “default” mode of pollution control.

SEE ALSO Pollution; Pollution, Air; Pollution, Water

BIBLIOGRAPHY

Alper, Joe. 1991. Antinoise Creates the Sounds of Silence. Science 252 (5005): 508–509.

Clark, Charlotte, and Stephen A. Stansfeld. 2005. The Effect of Aircraft and Road Traffic Noise on Children’s Reading. Literacy Today 44 (9): 24–25.

Evans, Gary W., et al. 2001. Community Noise Exposure and Stress in Children. Journal of the Acoustical Society of America 109 (3): 1023–1027.

Havas, Valerie. 2006. Noise! The Invisible Pollution. Current Health 2 32 (5): 10–11.

Lai, Patrick. 1996. Noise Pollution. In Major Environmental Issues Facing the 21st Century, eds. Mary K. Theodore and Louis Theodore, 389–396. Upper Saddle River, NJ: Prentice Hall.

Lusk, Sally, et al. 2004. Acute Effects of Noise on Blood Pressure and Heart Rate. Archives of Environmental Health 59 (8):392–399.

Staples, Susan L. 1997. Public Policy and Environmental Noise:Modeling Exposure or Understanding Effects. American Journal of Public Health 87 (12): 2063–2067.

U.S. Environmental Protection Agency, Office of Noise Abatement and Control. 1978. Noise: A Health Problem. http://www.nonoise.org/library/epahlth/epahlth.htm.

World Health Organization. 2001. Fact Sheet No. 258. Geneva:WHO Press. http://www.who.int/mediacentre/factsheets/fs258/en/.

Mathew Forstater

Noise Pollution

Noise pollution is the intrusion of unwanted, uncontrollable, and unpredictable sounds, not necessarily loud, into the lives of individuals of reasonable sensitivities. Using the "reasonable person" standard removes the notion that the judgment of sounds as unwanted is subjective. Unwanted sounds or noises can be traced back to Old Testament stories of very loud music and barking dogs as well as to ancient Rome where city residents complained about noisy delivery wagons on their cobblestone streets. The Industrial Revolution, the growth of cities, and the demand for transportation made the world even noisier. With the modern world so dependent on and enchanted with noise-producing and noise-related technology—automobiles, aircraft, helicopters, motorcycles, snowmobiles, jet skis, leaf blowers, amplified music, bass-driven car stereo systems—the ambient noise level is rapidly accelerating. This growth in noise has led to research examining the impact of noise on the lives and activities of reasonable people. The result has been a body of evidence that strongly suggests noise is hazardous to good mental and physical health.

To understand noise, one must know something about sound and how loudness is measured. Sound that travels through the air in waves has two major properties: the frequency or speed at which the waves vibrate and the intensity of each vibration. It is the intensity, or how many molecules are packed together with each vibration, that for the most part produces the sense of loudness, although frequency also contributes to the determination of loudness, with higher-pitched sounds sounding louder. Loudness is measured by a decibel scale (expressed as dB), but to reflect human hearing more accurately a modified version of this scale, known as the A scale, has been developed. On the A scale, loudness is measured in dBAs. The scale increases logarithmically so that an increase of 10 dB indicates a doubling of loudness, and an increase of 20 dB represents a sound that is four times louder. Whispers measure 20 dBA, normal conversation 50 to 60 dBA, shouting 85 dBA, and loud music over 120 dBA. Continuous exposure to sounds over 85 dBA may cause permanent hearing loss.

Exposure to very loud sounds that are enjoyable, and not technically noise to the listener, can lead to hearing impairment. Because many people, especially young children and teenagers, are not aware of the dangers of very loud sounds to their hearing, they should be warned that playing computer games with loud audio attachments, setting headsets at consistently high volume, or regularly playing ball in a loud gymnasium may affect their hearing over time. A survey of hearing threshold shifts among youngsters between the ages of six and nineteen found that one out of eight of them suffered a noise-related hearing problem. Children attending loud movies and sporting events, or visiting video arcades may be unwittingly exposing themselves to dangerously loud sounds. Teenagers are especially vulnerable as they are more likely to equip their cars with high-powered "boom boxes," attend loud dance clubs, and work in noisy fast-food restaurants.

Sounds need not be very loud to be deemed intrusive—for example, the drip of a faucet, an overhead jet, or a neighbor's stereo late at night. Noises are especially bothersome at night when one is trying to sleep, and a good night's sleep is vital to good health. Exposure to bothersome noises over time can be stressful, resulting in adverse health effects, such as hypertension. Although more research is needed to solidify a noise and health link, there is agreement that noise lessens the quality of life. Noises can be especially harmful to children. Scientific research indicates that noisy homes slow down cognitive and language development in young children. In addition, children living and attending schools near noisy highways, railroads, and airports have lower reading scores, and some children living or attending a school near a major airport have experienced elevated blood pressure.

In 1972 the U.S. government passed legislation recognizing the growing danger of noise pollution. It empowered the Office of Noise Abatement and Control (ONAC) within the Environmental Protection Agency (EPA) to curtail noise levels, but by 1982, during the Reagan administration, the office lost most of its funding. States and cities were no longer supported in their efforts to abate noise, and ONAC no longer published materials educating people on the dangers of noise. Recently, the federal government has passed legislation to lessen noise in national parks, for example, banning snowmobiles, but states and cities are on their own in controlling noise, with some cities more successful than others. Traffic noise, especially aircraft noise, is the major source of annoyance calling for better federal regulation within the United States. In contrast, the European Union is finalizing a noise directive that will require member states to produce noise maps and develop action plans to reduce noise levels.

Noise from snowmobiles, jet skis, and supersonic jets has also intruded on the environment, affecting animals' abilities to communicate, protect their young, and mate. Worldwide, antinoise groups believe their governments are doing too little to lessen the surrounding din, and groups from the United States, Europe, Canada, Australia, Africa, and Asia have joined together to educate both the public and governments about the long-term dangers of noise pollution, urging them to lower the decibel level. A quieter, healthier environment is within our grasp.

Bibliography

bronzaft, a.l. (1998). "a voice to end the government's silence on noise." hearing rehabilitation quarterly 23:6–12, 29.

bronzaft, a.l., and dobrow, s.b. (1988). "noise and health: a warning to adolescents." children's environments quarterly 5:40–45.

chen, a.c., and charuk, k. (2001). "speech interference levels at airport noise impacted schools." sound & vibration 35(7):26–31.

evans, g.w., and lapore, s.j. (1993). "nonauditory effects of noise on children. a critical review." children's environments 10:31–51.

federal interagency committee on aviation noise (fican). (2000). fican position on research into effects of aircraft noise on classroom learning. washington, d.c.

niskar, a.s.; kiezak, s.m.; holmes, a.; esteban, e.; rubin, c.; and brody, d.j. (2001). "estimated prevalence of noise induced hearing threshold shifts among children 6 to 19 years of age. the third health and nutrition examination survey. 1988–1994." pediatrics 108:40–43.

stansfeld, s.; haines, m.; and brown, b. (2000). "noise and health in the urban environment." reviews of environmental health 15:43–82.

internet resources

league for the hard of hearing web site. available from http://www.lhh.org/noise.

noise pollution clearinghouse web site. available from http://www.nonoise.org.

Arline L. Bronzaft

Noise pollution

Every year since 1973, the U.S. Department of Housing and Urban Development has conducted a survey to find out what city residents dislike about their environment . And every year the same factor has been named most objectionable. It is not crime, pollution , or congestion; it is noise--something that affects every one of us every day.

We have known for a long time that prolonged exposure to noises, such as loud music or the roar of machinery, can result in hearing loss. Evidence now suggests that noise-related stress also causes a wide range of psychological and physiological problems ranging from irritability to heart disease. An increasing number of people are affected by noise in their environment. By age forty, nearly everyone in America has suffered hearing deterioration in the higher frequencies. An estimated ten percent of Americans (24 million people) suffer serious hearing loss, and the lives of another 80 million people are significantly disrupted by noise.

What is noise? There are many definitions, some technical and some philosophical. What is music to your ears might be noise to someone else. Simply defined, noise pollution is any unwanted sound or any sound that interferes with hearing, causes stress, or disrupts our lives. Sound is measured either in dynes, watts, or decibels. Note that decibels (db) are logarithmic; that is, a 10 db increase represents a doubling of sound energy.

Noises come from many sources. Traffic is generally the most omnipresent noise in the city. Cars, trucks, and buses create a roar that permeates nearly everywhere. Around airports, jets thunder overhead, stopping conversation, rattling dishes, some times even cracking walls. Jackhammers rattle in the streets; sirens pierce the air; motorcycles, lawn-mowers, snowblowers, and chain saws create an infernal din; and music from radios, TVs, and loudspeakers fills the air everywhere.

We detect sound by means of a set of sensory cells in the inner ear. These cells have tiny projections (called microvilli and kinocilia) on their surface. As sound waves pass through the fluid-filled chamber within which these cells are suspended, the microvilli rub against a flexible membrane lying on top of them. Bending of fibers inside the microvilli sets off a mechanico-chemical process that results in a nerve signal being sent through the auditory nerve to the brain where the signal is analyzed and interpreted.

The sensitivity and discrimination of our hearing is remark able. Normally, humans can hear sounds from about 16 cycles per second (hz) to 20,000 hz. A young child whose hearing has not yet been damaged by excess noise can hear the whine of a mosquito's wings at the window when less than one quadrillionth of a watt per cm² is reaching the eardrum.

The sensory cell's microvilli are flexible and resilient, but only up to a point. They can bend and then spring back up, but they die if they are smashed down too hard or too often. Prolonged exposure to sounds above about 90 decibels can flatten some of the microvilli permanently and their function will be lost. By age thirty, most Americans have lost 5 db of sensitivity and cannot hear anything above 16,000 Hertz (Hz); by age sixty-five, the sensitivity reduction is 40 db for most people, and all sounds above 8,000 Hz are lost. By contrast, in the Sudan, where the environment is very quiet, even seventy-year-olds have no significant hearing loss.

Extremely loud sounds—above 130 db, the level of a loud rock band or music heard through earphones at a high setting—actually can rip out the sensory microvilli, causing aberrant nerve signals that the brain interprets as a high-pitched whine or whistle. Many people experience ringing ears after exposure to very loud noises. Coffee, aspirin, certain antibiotics, and fever also can cause ringing sensations, but they usually are temporary.

A persistent ringing is called tinnitus. It has been estimated that 94 percent of the people in the United States suffer some degree of tinnitus. For most people, the ringing is noticeable only in a very quiet environment, and we rarely are in a place that is quiet enough to hear it. About 35 out of 1,000 people have tinnitus severely enough to interfere with their lives. Sometimes the ringing becomes so loud that it is unendurable, like shrieking brakes on a subway train. Unfortunately, there is not yet a treatment for this distressing disorder. One of the first charges to the Environmental Protection Agency (EPA) when it was founded in 1970 was to study noise pollution and to recommend ways to reduce the noise in our environment. Standards have since been promulgated for noise reduction in automobiles, trucks, buses, motorcycles, mopeds, refrigeration units, power lawn-mowers, construction equipment, and airplanes. The EPA is considering ordering that warnings be placed on power tools, radios, chain saws, and other household equipment. The Occupational Safety and Health Administration (OSHA) also has set standards for noise in the workplace that have considerably reduced noise-related hearing losses.

Noise is still all around us, however. In many cases, the most dangerous noise is that to which we voluntarily subject ourselves. Perhaps if people understood the dangers of noise and the permanence of hearing loss, we would have a quieter environment.

[William P. Cunningham Ph.D. ]

RESOURCES

BOOKS

Chatwal, G. R., ed. Environmental Noise Pollution and Its Control. Columbia: South Asia Books, 1989.

Energy and Environment 1990: Transportation-Induced Noise and Air Pollution. Washington, DC: Transportation Research Board, 1990.

OECD Staff. Fighting Noise in the Nineteen Nineties. Washington, DC: Organization for Economic Cooperation and Development, 1991.

PERIODICALS

Bronzaft, A. "Noise Annoys." E Magazine 4 (March-April 1993): 16–20. O'Brien, B. "Quest for Quiet." Sierra 77 (July-August 1992): 41–2.