Modern life has given rise to a new form of pollution called noise pollution or sound pollution. Noise can be defined as “unwanted, unpleasant and disagreeable sound that causes discomfort”. Sound is an integral part of nature, but noise is unwanted sound without agreeable musical quality. The intensity of sound is measured in decibel (dB). One decibel is the faintest sound which a human ear can hear. Sound beyond 80 decibel harms hearing system and can be safely regarded as a pollutant. Frequency of sound is expresses in hertz (Hz). One Hz is equal to one vibration per second. People can hear sound from 16 Hz to 20,000 Hz.

Sources of sound pollution

The main contributors to noise are factories and industries, transportation and community and religious activity. It will not be an exaggeration to say that we Indians are a noisy people. All religious occasions, elections and family celebrations are manifested in a noisy manner.

The chief man-made sources in urban areas are automobiles, factories, industries, trains and aeroplanes. Noise makers are horns, sirens, musical instruments, TV, VCR, radio, transistor, telephone, dogs, loud speakers, washing machines, vacuum cleaners, food mixers, grinders, pressure cookers, fans, coolers and water pumps.

Effects of sound pollution

The different effects of noise pollution are categorized as auditory effects and non-auditory effects.

Auditory effects: These include auditory fatigue and deafness. Auditory fatigue appears in 90 dB and may be associated with side effects as whistling and buzzing in ears. Deafness can be caused due to continuous noise exposure. Temporary deafness occurs at 4000- 6000 Hz. Permanent loss of hearing occurs at 100 dB. Mumbai and Calcutta are the noisiest cities of the world. Many persons have risk of deafness in the big cities. Soldiers suffer hearing loss from loud noises of tank, artillery, helicopters and jet aircrafts.

Non-auditory effects: These are interference with speech communication, annoyance, and loss of working efficiency, physiological and psychological disorders.

-         Noise mainly interferes with man’s communication. It prevents us from what we want to hear and enjoy. It is easy to visualize a conversion carried out with whisher in a quiet place, while one has to shout for the same in a noisy factory.

-         Balanced persons express great annoyance at even low level of noise as crowd, highway, radio etc. The effects are ill temper and bickering.

-         Noise develops tiredness and those doing mental work may put to deterioration in their efficiency or even complete loss of ability to work.

-         Noise is responsible for disturbing the whole biological system. Anxiety, stress-reaction, fright are the effect of noise pollution. These reactions produce increase rate of heart beat, constriction of blood vessels, digestive spasm, dialation of pupil of the eye. It may cause damage to heart, kidneys, and liver and may also produce behavioral and emotional disturbances. The other physiological disorders are neurosis, insomnia, hypertension, and increase in sweating, hepatic diseases, giddiness and peptic ulcer. It is reported that blood is also thickened by excessive noises. Changes in breathing amplitude have also been reported due to loud noise.

-         Brain is also adversely affected by loud and sudden noise such as that of jet and aeroplane noise etc. People are subjected to psychiatric illness. It is also injurious to the health of pregnant woman and foetus. It has been recently reported that deformed babies are born due to excessive noise pollution.

Control of sound pollution

The following steps should be taken to control and minimize noise pollution.

-         Noise at source can be reduced by designing silencing devices in aircraft engines automobiles, industrial machines and home appliances. For example, the noise from a fan can be reduced by increasing the number of blades or by decreasing the rotational speed without any reduction in the air flow.

-         Noise creating machinery and equipment may be covered with insulating materials.

-         Workers in industries should use ear plugs or they may wear ear muffs.

-         Noise can be minimized in factories by covering the walls of the rooms with sound absorbers like acoustic tiles.

-         Enclosures can be constructed around industrial machinery.

-         Noisy operations should be conducted in an open space, far from any residential colony.

-         Trees absorb and dissipate sound energy. Plants and trees should be planted along highways, streets and near industrial areas. In metropolitan cities, green belt vegetation may have a great value in sound absorption.

-         Airport noise can be reduced by zoning the area so that no one is allowed to construct any house or factory within 10 km of the airport.

-         A big green belt of Ashok or Neem trees or forest around a jet port will not only absorb the noise but also purify the air and soil.

-         Road traffics should be restricted from unnecessary blowing of horns. Bus, car and truck drivers should be instructed not only for exceeding speed limit but also not to exceed noise limit from 82 dB.

-         The old vehicles making a lot of rattling noise should delicensed.

-         Silence zone must be created near schools, colleges and hospitals.

-         Noise pollution can also be checked by making new highways and circular roads without touching the towns and cities too closely.

-         Public must be made aware and educated about noise pollution and its effects through news, media, radio, TV and other programmes.

-         People can reduce indoor as well as neighbourhood noise by keeping the volumes of their radio, TV’s and VCR’s low and discarding the use of loud speakers on all occasions including marriage and birthday parties.

-         Noise pollution can be controlled through legislation. In India we have Motor Vehicles Act which provides restriction on trucks using double sirens while passing through some localities.

-         There is provision in the Indian Penal Code for checking nuisance. These are section 268 and 290. Fortunately noise has now been included under Air Pollution in air Pollution Control Act.

In our country, there have been several legislative measures for protecting the environment, even before independence, both at the state and central government level. However, the real awareness for environmental protection at global level was recognized at the United Nations Conference on the Human Environment held at Stockholm in June 1972. Keeping in view the need foe environmental protection, the Indian Parliament have taken various legislative measures.