Noise is defined as unwanted sound. Its intensity is measured in decibels (dB). Zero dB is defined as the weakest noise that a person with normal hearing can just barely detect in quiet surroundings, 55 dB is equivalent to light traffic sounds, and 120 dB is equivalent to jet takeoff from 200 feet away. Most behavioral studies use a modified dB scale, called the dBA scale, devised to approximate perceived loudness. This scale assigns higher weights to high-frequency sounds, since they are perceived as louder than low-frequency sounds of equal sound pressure.
Noise pollution is a worrisome problem in the United States. The Environmental Protection Agency (EPA) has estimated that more than 70 million Americans live in neighborhoods noisy enough to be annoying and to interfere with communication and sleep. More than 50% of production workers are exposed to workplace noise loud enough to damage hearing.
Noise is by definition unwanted and therefore frustrating and tension-inducing. As a stressor, it alters the functioning of cardiovascular, endocrine, respiratory, and digestive systems, and is also suspected of having damaging effects on mental health.
The hearing loss effects of noise are well established. The EPA estimates that 1 out of every 10 Americans is exposed to noise levels of sufficient intensity and duration to create permanent hearing losses. Hearing losses do not hurt and are not immediately apparent, but even minor hearing impairments seem to enhance susceptibility to further injury in the middle and late years.
The consequences of noise on performance cannot easily be predicted. They depend on the noise, the performance, the meaning of the sound, and the social context of the person performing. If people have clear warning of the need to react and receive easily visible cues, loud noise shows little or no overall effects on their work. In general, novel or unusual noises are more bothersome than familiar noise. However, familiar noises louder than 95 dBA—especially if unpredictable, uncontrollable, and intermittent—are disruptive. Typically, noise leads to variable performance— moments of inefficiency interspersed with normal and compensatory spurts of efficient performance. The lapses make workers more accident prone.
In academic settings, adverse effects have been documented repeatedly by well-controlled studies that take into account the socioeconomic and racial characteristics of the participants and use comparison groups. Among the effects of noisy homes and schools are impairment of auditory and visual discrimination, reading and visual-motor skills, overall scholastic achievement, and persistence in the face of frustration. One explanation for these effects is that noise disrupts the teaching-learning process, resulting eventually in cumulative deficits. Some investigators believe that the stressful effects of noise are ameliorated when people have accurate expectations about or (at least perceived) control over the noise.
Noise levels influence people's social conduct, as well. A number of experimental studies have found that individuals exposed to noise tend to be less helpful than those not exposed. Sheldon Cohen has suggested that noise causes subjects to focus their attention on salient aspects of the situation so they fail to notice interpersonal cues. Alternatively, decreases in helping might result from feelings of anger or frustration.
L. L. Davidoff
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