Monday, November 4, 2013

Noise pollution - Causes, types, effects and control of noise pollution

Noise pollution
Noise is defined as, "the unwanted, unpleasant or disagreeable sound that causes discomfort to all living beings". Sound intensity is measured in decibels (dB), that is the tenth part of the longest unit Bel. One dB is the faintest sound that a human ear can hear.

TYPES OF NOISE: Environmental noise has been doubling every ten years. Noise is classified as:
  1. Industrial Noise
  2. Transport  Noise and
  3. Neighbourhood noise
Industrial Noise: It is sound with a high intensity sound caused by industry machines. Sources of such noise pollution is caused by machines from machines in various factories, industries and mills. Noise from mechanical saws and pneumatic drills is unbearable and a nuisance to the public.
The Indian Institute of Oto-Rino Laryngology, Chennai reported that increasing industrial pollution damages the hearing ability by atleast 20%.
Workers in steel industry, who work close to heavy industrial blowers are exposed to 112dB for eight hours suffer from occupational pollution.

Transport Noise: Transport noise mainly consists of traffic noise from road, rail and aircraft. The number of automobiles on roads like motors, scooters, cars, motor cycles, buses, trucks and diesel engine vehicles have increased enormously in the recent past further aggravating the problem of transport noise.
Noise levels in most residential areas in metropolitan cities is hovering around the border line due to increased vehicular noise pollution. This high level of noise pollution leads to deafening in the elderly.

Neighbourhood noise: This type of noise includes disturbance from household gadgets and community. Common sources being musical instruments, TV, VCR, Radios, Transistors, Telephones, and loudspeakers etc. Statistically, ever since the industrial revolution, noise in the environment has been doubling every ten years.

Effects of Noise pollution
  1. Noise pollution affects both human and animal health. It leads to:
        1. contraction of blood vessels
        2. making skin pale
        3. excessive adrenalin in the blood stream which is responsible for high blood pressure.
        4. Blaring sounds are known to cause mental distress
        5. Heart attacks, neurological problems, birth defects and abortion
  2. Muscle contraction leading to nervous breakdown, tension, etc
  3. The adverse reactions are  coupled with a change in hormone content of blood, which in-turn increases  heart beat, constriction of blood vessels, digestive spams and dilation of the pupil of the eye.
  4. Adverse affects health, work efficiency and behaviour. Noise pollution may cause damage to the heart, brain, kidneys, liver and may produce emotional disturbance.
  5. The most immediate and acute effect of noise is impairment of hearing that diminishes some part of the auditory system. Prolonged exposure to noise of certain frequency pattern leads to chronic damage to the inner ear.
  6. Impulsive noise may cause psychological and pathological disorders
  7. Ultrasonic sound can affect the digestive, respiratory, cardiovascular system and semicircular canals of the internal ear.
  8. The brain is adversely affected by loud and sudden noise by jets and airplanes. People are subjected to psychiatric illness.
  9. Recent reports suggest that blood is thickened by excessive noise.
  10. The optical system of human beings is also affected by noise pollution. Severe noise pollution causes:
    1. Pupullary dilation
    2. Impairment of night vision and
    3. Decrease in rate of colour perception
Control measures:
  1. SOURCE CONTROL: This includes source  modification such as acoustic treatment to machine surface, design changes, limiting operational timings, etc
  2. TRANSMISSION PATH INTERVENTION: This includes containing the source inside a sound insulating enclosure, constructing a noise barrier or provision of sound absorbing materials along the path.
  3. RECEPTOR CONTROL: This includes protection of the receiver by altering the work schedule or provision of personal protection devices such as ear plugs for operating noisy machinery. The measure may include dissipation and deflection methods.
  4. OILING: Proper oiling will reduce noise from the machine.
Preventive measures:
  1. Prescribing noise limits for vehicular traffic
  2.  Ban on honking (usage of horns) in certain areas
  3. Creation of silence zones near schools and hospitals
  4. Redesigning buildings to make them noise proof
  5. Reduction of traffic density in residential areas
  6. Giving preference to mass public transport system.

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