Noise Pollution

The human ear is constantly being assailed by man made sounds from all sides, and there remain few places in populous areas where relative quite prevails. What do aeroplanes, trains, car and pneumatic drills, and radio and television sets have in common? They all produce noise, the most dangerous pollutant of humans environment. nice has become a permanent part of our lives these days because of the development of machinery, industry and technology. Noise harms the body and mind. Noise not only cause irritation or annoyance but it constricts your arteries, increases the flow of adrenaline and forces your heart to work faster.

The word noise is usually defined as unwanted or unpleasant sound that causes discomfort. Noise is also defined as "wrong sound, in the wrong place at the wrong time". Noise pollution means "the unwanted sound dumped into the atmosphere leading to health hazards".

Formerly noise was limited only to the industry. This too was not much as there were only few industries. These bhej there has been rapid industrial growth. More ever, there has been population explosion, due to which there is heavy traffic, urban crowd and electric equipment. All these have added to the night nuisance in environment. In our country, besides these the two other factors are religious and social functions which increase the gravity of situation. 

Sources of noise

The main contributors to noise are factories and industries transportation and community and religious activities. there should not be an exaggeration to say that we Indians are energy per and every sentiment and location is manifested in a noisy manner - be it a religious occasion, elections or a family celebration.

The chief man made sources in urban areas are automobiles, factories, industries, trains, aeroplanes. Noise makers are horns,  sirens, lawn movers,  musical instruments, TV, radio, transistors, telephone, dogs, loudspeakers, washing machines, vacuum cleaner, food mixers, pressure cookers, fans, air conditioners, air coolers. Ever since the industrial revolution, there has been doubling every 10 years of environmental noise.

Properties

There are two basic properties of sound, (1) loudness and (2) frequency.

Loudness is strength of sensation of sound perceived by the individual. It is measured in terms of decibels. Just audible sound is about 10 dB, a whisper about 20 dB, library place 30 dB, normal conservation 35 to 60 dB, heavy Street traffic 60 to 80 dB, boiler factories 120 dB, jet planes (take off) about 150 dB, rocket engine about 180 dB. The loudest sound a person can stand without much discomfort is about 80 dB. Sounds beyond 80 dB can be safely regarded as pollutant as it harms hearing system. The WHO has fixed 45 dB as the safe noise level for a city. For international standards a noise level up to 65 dB is considered tolerate. Mumbai, New Delhi, Kolkata and Chennai usually register more than 90 dB. Loudness is also expressed in sones. One sone equals the loudness of 40 dB sound pressure at 1000 hz.

Frequency is defined as the number of vibrations per second. It is denoted by Hertz (hz). 1 hz equals to 1 vibration per second. People can hear sound from 16 (infra audible) to 20000 (ultrasonic) hz.

Effects of noise pollution

The different effects are categorised as (1) auditory effects (affecting hearing faculty) and (2) non auditory effects (other than auditory ones).

Auditory effects

These include auditory fatigue, and deafness. Auditory fatigue appears in the 90 dB and may be associated with the side effects as whisling and buzzing in ears. Deafness can be caused due to continuous noise exposure. Temporary deafness occurs at 4000 to 6000 hz. Permanent loss of hearing occurs at 100 dB. Mumbai and Kolkata are the noisiest cities in the world. Many persons have risk of deafness.

Non auditory effects

These are interference with speech communication, annoyance, laws of working efficiency and physiological disorders. 

Interference with speech communication

A noise of 50 to 60 dB commonly interferes with speech; sound of warning signals may be misunderstood.

Annoyance

Balance person express great annoyance at even low level of noise as crowd, highway, radio etc.

Loss in working efficiency

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

Physiological disorders

There develop a number of physiological disorders due to imbalance in functioning of the body. These are neurosis, anxiety, insomnia, hypertension, hepatic diseases, behavioural and emotional stress, increase in sweating, giddiness, nausea, fatigue etc. Noise also cause visual disturbance, and reduce depth and quality of sleep does affecting overall mental and physical health. Other effects are undesirable changes in respiration, circulation of blood in skin and gastrointestinal activity.  Noise pollution also causes incidence of peptic ulcers.

                                                                              Continuous noise causes an increase in cholesterol level resulting in the constriction of blood vessels making you prone to heart attack and strokes. There may be still births and usually low weight children born to mothers living near airports.

Supersonic airplanes create a shock wave called Sonic boon, which produces a startle effect that can be  more harmful than a continuous noise. The Sonic boon may spread in an area of 10 to 80 miles and when it hits the ground it damages window pans and building structures. This may also faster in the human foetus heartbeat rate.