Occupational and Community Noise
In ancient Rome, the clatter of iron wheels on stone pavements disturbed people's sleep and so annoyed citizens that legislation was enacted to control movement. Some cities of medieval Europe prohibited horse and carriage traffic to protect the sleep of the inhabitants.
The noise problems of the past, though, are not comparable to those plaguing modern society: the roar of aircraft, the thunder of heavily laden trucks, and the thumps and whines of industry. Such noise can be not only annoying but also damaging to the health, and it is increasing with economic development.
The recognition of noise as a serious health hazard (as opposed to a nuisance) is a recent development, but the following effects are being remarked:
* Globally, some 120 million people are estimated to have disabling hearing difficulties.
* In 1990, about 30 million people in the United States were exposed daily to occupational noise levels above 85 decibels (dB), compared with more than nine million people in 1981; these people are mostly in the production and manufacturing industries.
* Prolonged or excessive exposure to noise, whether in the community or at work, can cause permanent medical conditions, such as hypertension and ischemic heart disease.
* Noise can adversely affect performance--for example, in reading, attentiveness, problem solving, and memory Deficits in performance can lead to accidents.
* Noise above 80 dB may increase aggressive behavior.
* A link between community noise and mental-health problems is suggested by the demand for tranquilizers and sleeping pills, the incidence of psychiatric symptoms, and the number of admissions to mental hospitals.
Noise levels associated with impairment may be experienced at open-air concerts, discotheques, motor sports events, and so forth. For most people, however, a lifetime of continuous exposure to an average noisy environment (70 dB) will not cause hearing impairment. An adult person's ear can tolerate an occasional noise level of up to 140 dB, but for children, such exposure should never exceed 120 dB.
Sources of indoor noise are ventilation systems, office machines, home appliances, and neighbors. Some typical sources of more general neighborhood noise include restaurants, live or recorded music, sports, playgrounds, car parks, and barking dogs.
The major sources of noise that damages hearing are impact processes, materials handling, and industrial jets. Air jets--widely used for cleaning, drying, power tools, and steam valves--can generate sound levels of 105 dB. In the woodworking industry the sound levels of saws can be as high as 106 dB. …