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| Last Updated:: 23/04/2013



         Sound is a form of energy which travels in the form of waves. The waves are created when molecules in air undergo compression and rarefaction alternately. Sound waves move outward from the vibrating source. The unwanted sound is known as noise. The word noise comes from the Latin word nauseas meaning seasickness. A decibel (dB) is the standard for the measurement of noise. Noise can originate from a variety of sources. These sources can be natural or man made. The natural sources could be thunder, sea-shores etc. but exposure to them is not very regular and the number of people exposed to it form only a small percentage of the total population. Noise pollution caused by man made sources is the major contributor and needs urgent attention. These sources include industries, domestic sources, transport and traffic, construction activities, festivals and religious activitis etc.WHO suggests that noise can affect human health in a number of ways. These include


  • Physical effects: These are high blood pressure, other cardiovascular changes, problems in digestive system and general fatigue. Prolonged exposure to noise levels 80decibels (dB) and above can cause deafness.
  • Physiological effects:These arise due to interference in the biological functioning of the body due to noise pollution. They include anxiety, insomnia, hypertension, nausea and giddiness. Noise levels in the range 120-150 dB can affect respiratory system and cause dizziness, loss of physical control etc. A loud noise can also cause increased secretion of hormones of the pituitary gland viz. Adrenocorticotropic hormone (ACTH), which stimulates adrenal gland for further secretion of several other hormones. This chain of secretions enhances sensitivity of the body to adrenalin, increase in level of blood sugar, suppression of immune system and a decrease in the ability of liver to detoxify blood. Chronic noise may also lead to abortions and congenital defects. Frequent exposure to noise levels 85 dB or above can lead to increased pulse rate, higher cholesterol levels and violent behavior. The noise levels of 70dB can cause constriction of blood vessels in skin. .
  • Psychological effects:These include loss of working efficiency resulting in reduced output, absentism and higher rates of accidents and injuries. Noise can also interfere with sleep which in turn affects overall mental and physical health of a person. Noise levels of 45-50 dB can cause changes in sleep patterns and affect deep sleep. Noise levels of 50-60 dB can also interfere with communication. At times, it may not be possible to hear warning signals. In addition to humans, noise can be equally adverse to wildlife also. Animals in the zoo are quite sensitive to the noise in their surroundings and their behavior can be affected by noise.

Control of Noise Pollution: Noise is a controllable pollutant. Noise pollution can be controlled by changing the vehicle design, changes in tyres or road surfaces and eliminating old and noisier vehicles can reduce noise due to surface transport. Similar changes in design of machinery and equipment used in industries and construction work can help in checking noise pollution. If possible the residential areas should be distant from railroads, highways, airports, industries and factories. Use of sound absorbing materials such as glass wool, felts, porous blocks, perforated files and blocks, carpets etc can also minimize noise. Noise barriers, mufflers,silencers etc. reduce the transmission of sound. In addition, earplugs, earmuffs and helmets can be used for personal protection from noise.

          A buffer zone of vegetation is also helpful to curtail noise to some extent. In addition to this, it is also necessary to educate people about noise and its harmful effects. Such an awareness would encourage them to exercise self control and reduce noise pollution. In India, various legal provisions are also initiated to control noise pollution. The Central Pollution Control Board (CPCB)constituted a Committee on Noise Pollution control. This committee recommended noise standards for ambient air, automobiles, domestic appliances and construction equipment. These standards as notified in Environment Protection Rules (1986) are given below.   


Day Time/dB

Night Time/dB

A.  Industrial Area



B.  Commercial Area



C.  Residential Area



D.  Silence Zone



(The day time is between 6 a.m. and 9 p.m. whereas night time is 9 p.m. to 6 a.m.)


Reference: Environmental Science by Ahluwalia V.K. And Sunita Malhotra (2009) 

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