Noise has been well defined as “unwanted sounds” which is being “dumped” into the atmosphere to disturb the unwilling ears. It adversely affects our physiological to disturb the unwilling ears. It adversely affects our physiological and mental health.
Measurement of Sound
Sensitivity of human ear is measured clinically with the audiometer. It is a frequency generator which produces different frequencies, intensities which are controlled by an attenuator. The audiometer test ranges usually from 250 Hz to 8000 Hz. The intensity or loudness of sound is measured on a scale called decibel scale or dB scale. It measures the loudness of sound in terms of relative units of energy or power on logarithmic scale according to the response of human ear. A threshold of hearing from 0 to 25 dB is considered normal hearing range for man.
Measurement of intensity of sound or noise in decibel, created by some common sources.
|0-20 dB||Just audible|
|20- 30 dB||Very quiet|
|70-90 dB||Moderately loud|
|90-110 dB||Very loud|
|110-120 dB||Uncomfortably loud|
|120-140 dB||Painfully loud|
Sources of Noise Pollution
- Various industries such textiles mills, printing presses, engineering establishments,
- Agricultural machines like tractors, harvesters, tubewells, lawn mowers,
- Defence equipment such as tanks, artillery, rocket launching, shooing practices, explosions,
- Entertaining equipment like radios, record players, television sets,
- Domestic gadgets such as desert coolers, air conditioners, vaccuum cleaners, exhaust fans, mixers, pressure cooker,
- Public address systems like loud speakers,
- Transport vehicles like scooters, motor cycles, car, buses, trucks, trains, jet planes,
- Dynamite blasting,
- Crackers used at occasions like marriages and festivals,
- Bull dozing, stone crushing, construction work, etc.
Effects of Noise Pollution
i. Effects on Hearing
Prolonged and continued high intensity noise not only cause some hearing loss but may cause a permanent loss of hearing. A sudden loud noise such as an explosion can damage the tympanic membrane (ear drum). Noise over 115 dB is regarded as highly avoidable. The World Health Organization (WHO) recommends an industrial noise limit of 75 dB. A type writer at work measures about 60 dB.
ii. Effect on General Health
Noise may cause stress, anxiety, headache (by dilating blood vessels of the brain), high blood pressure ( by increasing cholesterol level in the blood), increased heart beat, constriction of blood vessels, defective night and colour vision, emotional disturbances. Noise can impair the development of nervous system of unborn babies which leads to abnormal behavior in later life. It has been reported that prolonged noise pollution causes damage to heart, brain and liver in animals.