Every source of noise is a potential source of noise pollution: Traffic, airplanes, trains, air conditioners, heavy equipment and more all churn out noise. Some of these produce dangerous levels of noise on their own, but put together in a densely populated environment they can prove hazardous to human health. Noise pollution has been linked to, among other things, hearing loss, increased stress, high blood pressure, fatigue and sleeplessness.
The first step in controlling noise pollution is identifying all of the sources of sound pollution in a given area. This is called a survey and it is done by sampling the sound waves in the area being studied. Samples of decibel levels are taken from a variety of locations at different times of day and different days of the week. Noise levels are measured and the sources of noise identified.
Once sources are identified, efforts can be made to control the noise levels. This may include banning certain machines from certain areas. More frequently, though, it simply means placing certain restrictions on the use of certain devices. This may include limiting the times at which certain machines can be used, such as limiting the use of jackhammers or pile-drivers to daytime only. Air traffic provides another example of control: In most cities aircraft are directed around the core of the city and not allowed to fly directly over it so that they do not contribute to noise levels.
Some noise cannot be eliminated but can be reduced. Laws vary by state and sometimes by city, but in most locations mufflers are required to reduce engine noise. In many locations there are restrictions on the volume that a stereo can produce in a car or a home. Noise dampeners are also sometimes employed to reduce the spread of sound waves. Varieties of dampeners are available for a variety of electronics, and for construction sites. Dampening walls are also used in some locations to separate busy freeways from residential neighborhoods.
Where noise cannot be controlled or reduced, personal protection can be employed. OSHA requirements mandate that workers in certain high noise areas such as airports and some factories and construction sites wear headphones to block out dangerous noise levels. A variety of noise pollution controls are also available for homes and businesses. These include noise dampening insulation for walls and white noise generators which make a low level sound to help mask and drown out outside noise.