Noise pollution is unwanted, unpleasant, loud disturbing sound that has a harmful effect on human beings as well as animals. The frequency of sound is measured in Hz (Hertz). Range of human hearing is 50 Hz to 15000 Hz.
Infrasonic vibrations (i.e., below 50 Hz) can be felt because some body parts resonate at this frequency. Ultrasonic vibrations (i.e., above 15000 Hz) is used in imaging, cleaning, drilling, cutting, welding and sealing. The intensity of sound is the rate at which energy from the wave is transferred on to the surface per unit area. The unit of sound level is decibel.
Sources of noise pollution
Following are the main sources of noise pollution:
- Various industries such as textile mills, printing presses, engineering establishments cause noise pollution.
- Defence equipment such as tanks, artillery, rocket launching, shooting practices, explosions.
- Entertainment equipment like radios, record players, television also contribute to noise pollution.
- Various agricultural machines such as tractors, harvesters, tube-wells produce noise.
- Domestic gadgets such as desert coolers, air conditioners, vacuum cleaners, exhaust fans, mixers, pressure cooker, create a lot of noise.
- Transport vehicles such as motorcycles, scooters, cars, buses, trucks,trains, jet planes create a lot of noise.
- Public address systems such as loud speakers.
- Dynamite blasting also causes noise pollution.
- Crackers used at occasions such as marriages and festivals is also a source of noise pollution.
- Bull dozing, stone crushing, construction work, etc.
Effects of noise pollution
Following are some of the important effects of noise pollution:
1.Constant noise reduces the hearing capacity. It also produces severe and continuous headache. A sudden loud noise such as an explosion can damage the tympanic membrane (i.e., ear drum).
2. Noise causes headache by dilating blood vessels of the brain, eye strain by dilating the pupil, digestive spasms through anxiety and high blood pressure by increasing cholesterol level in the blood.
3. Noise above 90 decibel produces sudden flushing of skin, constriction in the muscles of stomach and creates excitement and anger in human beings.
4. Continuous noise also creates ulcers, heart diseases, high blood pressure, etc.
5. Noise releases larger amounts of adrenal hormones.
6. Noise can impair the development of nervous system of unborn babies which leads to abnormal behaviour in later life.
7. Pollution causes damage to heart, brain and liver in animals.
8. A sudden high intensity of sound produces a startle reaction which may affect psychomotor performance.
9. Besides it also causes cracks in the walls, etc.
Effects of noise on animals
Noise pollution produces a number of adverse effects on animals.
- Animals lose the ability to listen to stealth movement of enemies .
- High intensity sound disturbs the functioning of many internal organs including endocrine glands.
- Noise pollution disturbs the reproductive cycles of several insects.
- It disturbs egg laying of birds.
- Noise affects the development of embryo.
- Congenital defects appear in foetus or embryo of not only animals but also human beings.
- Noise pollution disturbs the hatching of birds.
Following are some of the preventive and curative measures to reduce the noise pollution:
Decibel meters and noise pollution laws:
Installation of decibel meters at different places, in order to monitor the level of noise pollution is helpful. Strict enforcement of noise pollution control laws are helpful in controlling sound pollution.
Heavy population areas consists of four zones -silence zone ( i.e., near hospitals, educational institutions), residential zone, commercial and industrial zone. This zonation proves to be very helpful in controlling noise pollution.
All types of machines whether industrial or engines of motor vehicles should be signed to produce lesser noise, maintained properly and lubricated from time to time. Low volume of loudspeakers and entertainment gadgets is a good measure to control noise pollution. Sound diversion devices are also available the deflect the sound.
a).The buildings should have a proper layout for reducing the intensity of sound coming from road side, commercial or industrial complex.
b). Growing and maintaining green belt of trees and shrubs around the residential areas as well as along rows of houses.
c). Covering of outer surface of the buildings with sound asbestos such as acoustic tiles and rough cement coating.
d). Use of rubber- plastic foams in ceilings and floors.
e). Acoustic furnishings inside the buildings.
Green muffler or Green belt vegetation:
Green muffler or green belt vegetation is the plantation of trees and shrubs in rows to serve as a noise absorber. It also reduces air pollution because the trees and shrubs absorb pollutant gases and cause settling of suspended particulate matter. Green muffler or green belt vegetation is specially planted along roads for absorption of noise pollutant gases and dust generated by moving vehicles.
Plantation around industrial complexes in the form of wider belts is helpful for insulating the residential and commercial complexes not only from sound, smoke, dust and gases but also from the accidental release of toxic gases. Green belt of trees and hedges around domestic units is helpful for protecting residential areas from outside noise and air pollution as well as similar pollution from individual dwelling units.
Earplugs and ear muffs:
Earplugs or ear muffs are of great use for traffic police personnel and factory workers who work in high noise pollution . They are devices which fit into ear canal for blocking sound waves. Ear plugs are of two types; permanent and disposable. Ear muffs are hard shells that are attached to head and cover the external ears completely in order to block sound waves entering the ears. Ear muffs contain fluids seals or plastic foam for absorbing sound.