What is noise pollution and why it is considered a source of pollution? People living in big cities are exposed every day to unwanted and harmful sounds such as loud cars and motorcycles, leaf blowers, barking dogs, noisy neighbors, parties, car alarms, police and firefighter sirens. It is common in many neighborhoods to hear people complaining about loud sounds disturbing their personal activities such as rest, sleep, study, entertainment, relaxation and conversation. A sound becomes unwanted when it either interferes with normal activities or disrupts or diminishes a person's quality of life. For example, in a noisy classroom, students may not be able hear the teacher and may become upset or fall behind in learning as a consequence.
How does noise pollution relate to engineering? Environmental engineers measure noise pollution and report recommendations for noise reduction or elimination. Noise control engineers specialize in designing and testing noise insulation technologies and sound-absorbent materials such as acoustical foam and glass fiber. Engineers in various fields ranging from mechanical, aeronautical, industrial, electrical to civil engineering share a common interest in noise pollution reduction. They design new technologies that produce less noise in order to meet recommended standards. Examples of noise protection products are noise neutralizers such as noise-cancelling headphones and noise insulation windows and doors.
Definition and measurement: Noise pollution refers to any unpleasant, damaging or irritating noise that has the potential to harm people, wildlife or the environment. The decibel (dB) is the main unit used to measure the intensity or loudness of sounds. A sound can also be measured by its pitch, which is the frequency of sound vibrations per second. For example, a low pitch produced by a deep voice, makes fewer vibrations per second than a high voice. Sounds with higher pitch, such as a cry or sound from a violin, have a high rate of vibrations. Sound is usually recorded with a microphone. However, in a sound level meter, a sound sensor is used. Sound sensors work like microphones but are much more accurate.
How does a sound sensor work? The response of a sound sensor to a nearby sound is approximately proportional to the sound pressure, which is the air pressure produced by the propagating sound. For example, if we talk with a piece of paper placed just in front of our mouth, the resulting air pressure causes the paper to move. A similar observation can be made by feeling vibrations from a loud speaker.
What are the sources of noise pollution? Most unwanted sounds are made by transportation vehicles such as airplanes, trains, cars, trucks, buses, motorcycles and construction site equipment such as pneumatic hammers, air compressors, bulldozers, loaders, dump trucks and pavement breakers. Noise can also come from household appliances such as music and television sets, air conditioning, refrigerator, lawn mowers, leaf blowers, loudly talking neighbors or a crowd of people.
Health hazard: According to the World Health Organization (WHO), exposure to levels of noise exceeding safe limits (anything over 50 decibels), can be detrimental to hearing and has the risk of contributing to high blood pressure, strokes and even heart attacks. In fact when the body is exposed to high levels of noise, it reacts by releasing stress hormones and keeping the body in a perpetual level of tension. Long time exposure to loud sounds may result in side-effects such as irritation and anger, lack of concentration, interrupted sleep and hearing-related damage such as tinnitus. The human ear feels pain at 120-140 decibels, and for that reason, we are tend to protect our ears with our hands when listening to sounds in or above that decibel range.
Environmental threat: Plants require cool and peaceful environments to grow, and noise pollution causes poor crop quality. Noise has ripple effects on long-lived plants such as trees and the consequences could last for decades, even after the source of the noise goes away, according to lead author Clinton Francis of the National Science Foundation. Birds and other animals change their behaviors in response to human noise, such as the din of traffic or the hum of machinery. Noise creates sound waves that indirectly weaken the edifice of buildings, bridges and monuments and over time, can put buildings in dangerous condition. (See more information at http://www.sciencedaily.com/releases/2012/03/120320195747.htm.)
Engineering controls: Due to the increasing concern about noise pollution, engineering controls are designed to eliminate or reduce the level of noise generated, isolate workstations exposed to excessive noise or insulate noisy work areas. For example, noisy equipment and machinery are replaced with newer models that are quieter or isolated in separate rooms equipped with sound-absorbent materials, dampers, mufflers, silencers or barriers. The same materials are used in construction to keep outside noise from coming into homes and classrooms. Today, most cars are equipped with mufflers, aircraft engines are designed to make less noise, and modern subway systems are less noisy.
decibel (dB): The SI (International System of Units) unit of measure of sound intensity.
environment: The air, water and land in or on which people, animals and plants live.
hertz (Hz): The SI unit of measure of frequency.
impairment: Physical or mental damage.
mean: Statistical unit computed as the sum of all measures divided by the number of records. Also known as the average.
noise: A sound of any kind.
noise pollution: Annoying or harmful noise.
pollution: An undesirable state of the environment.
sample: A small number of measures.
sensor: A device converting a physical factor into an electrical signal.
sound level meter: A device used to measure the noise intensity.
source: A point of origin or procurement.
Pre-Activity Survey: Before providing any information, ask students to complete the Measuring Noise Pollution Pre-Activity Survey to the best of their abilities. Reassure students that this is not for a grade so they feel comfortable writing down their ideas, even if they are unsure. Tell them that even if they do not know all the answers at the start of class, they will know them by the end of the activity.
Informal Discussion: Ask students some questions about the subject matter, covering the questions and correct answers to the pre-activity survey. Refer to the Measuring Noise Pollution Pre-Activity Survey Answer Key. Ask the students:
- What is pollution? Have you ever heard of noise pollution? What is noise pollution?
- What tools might we use to record sound? What can we use to measure sound level?
- What unit of measure do we use to measure sound level?
Activity Embedded Assessment
Analysis: While the experiments are being conducted, have students complete the Measuring Noise Pollution Worksheet and a bar graph of their data. Ask students to comment on the procedure to measure the sound intensity during each experiment. To make sure the graph is completed correctly, ask students what they must display on the horizontal axis and what they must display on the vertical axis. Check that students use an appropriate scale that can fit all the recorded data.
Formal Discussion: Ask students to explain the entire procedure in their own words, as if they were explaining the activity to a family member. In particular, ask them to explain noise pollution, its causes, the unit used to measure sound intensity, and the measurement tools used to measure sound levels. Expect students to be able to cite at least three sources of noise pollution, two health hazards related to noise pollution and two manufactured products to reduce noise pollution. Based on the noise levels they measured in the activity, ask students to list noise pollution sources they believe to be over 85 dB. Also discuss with students the role of each individual component in the experiment (that is, the sensor, the brick, the program and the graph).
Have You Heard? Noise Can Affect Learning!
A handful of research studies confirm that noise has a negative effect on a child's ability to learn. Also, "noise education" should be part of the school curriculum; kids should know how to protect their ears from harm.
Children in schools bombarded by frequent aircraft noise don't learn to read as well as children in quiet schools do, say Cornell University researchers. And those researchers have discovered one major reason: kids tune out speech in the racket.
"We've known for a long time that chronic noise is having a devastating effect on academic performance of children in noisy homes and schools," says Gary Evans, an environmental psychologist in Cornell's College of Human Ecology and an international expert on noise, crowding, and other forms of environmental stress.
Evans and his collaborator, environmental psychologist Lorraine Maxwell, compared children in a noisy school (in the flight path of a major international airport) with similar children in a quiet school. Their study, which will be published in Environment and Behavior later this year, compared a total of 116 first and second graders from two elementary schools. One school was battered by peaks of up to 90 decibels of noise from low-flying planes every 6.6 minutes. The other school, closely matched for ethnicity and percentage of children receiving subsidized school lunches and speaking English as a second language, was in the same urban area but in a quiet neighborhood.
The study's findings were significant for speech perception amidst noise, states a summary of the research. "This implies that language acquisition is an underlying mechanism that accounts for some of the noise-reading deficit link," says Maxwell.
Evans and Maxwell also suspect that other factors may be at work in noisy schools and neighborhoods, such as teacher and parent irritability and their reluctance to talk as much, use as many complete sentences, and read aloud as often as other teachers and parents do.
The research was supported by the Cornell College of Human Ecology; the National Heart, Lung, and Blood Institute; and the U.S. Department of Agriculture.
ADDITIONAL STUDIES OF NOISE AND LEARNING
- Preschoolers in daycare centers located near elevated trains in New York City did poorer on psychomotor skills than their counterparts in quieter neighborhoods did. (Hambrick-Dixon, Developmental Psychology, 1985)
- Older students who attended schools near major New York airports had lower reading scores than children in schools located further from the airports did. (Green & Shore, Archives of Environmental Health, 1982)
- Children living near noisy highways in Los Angeles had lower reading scores and children living near a major airport there had more difficulty solving cognitive problems. (Cohen, Glass and Singer, Journal of Experimental and Social Psychology, 1973 and 1980)
- In one New York City school, a study focused on students in grades two, four, and six. Half of the classes at each grade level were in classrooms adjacent to train tracks; the other half of the classes were on the quieter side of the building. The study showed that the reading levels of the students on the noisy side of the building were behind the reading levels of their peers on the quiet side of the building. The sixth graders on the noisy side of the building averaged as much as one year behind in reading. (Bronzaft & McCarthy, Environment and Behavior, 1975) Then rubber pads were installed on the nearby train tracks and acoustic ceiling tiles were installed on ceilings of the noisiest classrooms. Those noise-abatement measures cut the noise levels in the noisy classrooms by as much as eight decibels. (Noise levels are cut in half for every ten-decibel decrease in measured sound.) A two-year study following the installation of the rubber pads and acoustic tiles showed no differences in reading levels between classes on the two sides of the building. (Bronzaft, Journal of Environmental Psychology, 1981)
- A study of seventh and tenth graders found that the high-academic students were not affected by nearby airport noise while lower-achieving students were affected. (Maser, Sorensen, Kryter & Lukas, Western Psychological Association Conference, 1978)
- Noise is more bothersome in crowded classrooms; teachers in those classrooms might resort to quieter, less effective teaching methods because of the conditions. (Gifford, Environmental Psychology, Allyn and Bacon, Inc., 1987)
- Language and cognitive skills develop more slowly in children raised in noisy homes. Possible reason: Parents in noisy homes interact less often with their children. (Wachs, American Psychological Association Conference, 1982)
SO WHAT ABOUT NOISE?
More efforts should be made to ensure that the classroom environment is conducive to learning, experts say. In addition, schools must include in their curricula the information students need to know about noise and how it can affect their hearing and their health--and their studies! Many textbook companies are devoting more space to noise education now than they have in past editions, but many experts say that isn't enough. They say every state should mandate "noise education" as part of its health curriculum.
- The Mabaan Tribe of the Sudan This study found that older members of the Mabaan tribe of the Sudan had better hearing that 20-year-old men living in industrialized society. The quiet, rural environment in which the Mabaans live might account for their hearing superiority, the study says. In addition, young Mabaans (aged 15 to 35) had better hearing than their "civilized" peers. The conclusion: Exposure to noise at a young age might harm the hearing of children in industrialized societies. (Rosen, Plester, El-Mofty & Satti, Annual of Otology, Rhinology and Laryngology, 1962)
- Noise Can Be Harmful to Your Health Exposure to noise in the workplace or in the home (when the home is located near an airport, train line, highway, etc.) can cause stress of the kind known to result in cardiovascular and circulatory disorders. (Kryter, The Effects of Noise on Man, Academic Press, 1985; Tempest, The Noise Handbook, Academic Press, 1985)
- How Loud Is That Music? Researchers stopped people on the street who had headsets on. The researchers asked to measure the level of the sound the people were listening to. Most of the people were listening to sounds measured in excess of 110 decibels. [Note: That noise level is equivalent to the sound made by sandblasting or a loud rock concert.] (Madell, Hearing Rehabilitation Quarterly, 1986)
- A Study of 18,000 Students Audiograms from 18,000 students ages six to eighteen were studied. The study showed that the percentage of students with hearing loss increased steadily with age and that the loss was four times greater for boys than it was for girls. (Cozad, Marston & Joseph, Journal of School Health, 1974).
Story sources: Cornell University News Service and "Noise and Health: A Warning to Adolescents" by Arline L. Bronzaft and Stephen B. Dobrow, Children's Environments Quarterly, Summer 1988. Special thanks to Nancy Nadler of the League for the Hard of Hearing for providing information about these studies.
- Fun Quiz A quiz for kids about noise from the League for the Hard of Hearing.
- Stop That Noise! A description of an educational program from the League for the Hard of Hearing that provides students with information about noise and its effects on hearing.
- Noisy Toys Some toys are not as much fun as they look. Many toys designed to stimulate our children can be dangerously loud. Some examples from the League for the Hard of Hearing.
- Noise and Hearing Loss The official "National Institutes of Health Consensus Development Conference Statement" on noise and hearing loss; what causes it; which sounds can damage hearing; and what can be done to prevent hearing loss.
- Noise, Ears, and Hearing Protection Q & A about noise and hearing loss from the American Academy of Otolaryngology.
- Noise On the Farm Test your awareness of noise on the farm and learn how to reduce the risk of hearing loss from farm noises.
- The #1 Reason Kids Go to the Doctor: Ear Infections Good Housekeeping's look at the increasing number of kids with ear infections, the causes and consequences of ear infections, and what parents can do to minimize the risk.
- More Internet Links Additional links provided by the League for the Hard of Hearing.
Article by Gary Hopkins
Education WorldÂ® Editor-in-Chief
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