Sound that is unpleasant and irritating is called noise. Noise pollution is common in busy towns, cities, mining and industrial centres, and airfields. It is mainly caused by our activities. Sources that produce noise are motor vehicles, aeroplanes, machinery, televisions, radios, pets and humans.
The loudness of sound is measured in decibels (dB). Noise that goes on continuously for a long time can make us tired and irritable, give us a headache, and prevent us from sleeping properly. Over long periods, this kind of strain can cause illness , especially mental illness. Noise is also linked to high blood pressure and coronary heart disease. Constant exposure to noise above 85 dB can cause permanent loss of hearing. Sudden explosive noise over 150 dB may cause deafness.
In quarries, airports and factories where noise levels cannot be reduced, the workers are advised to wear ear muffs as a precaution to prevent loss of hearing or deafness.
