It is clear, however, that noise, even though a "non-specific stressor", does cause a physical response. It elicits the same responses as a perceived physical threat would produce: it activates the nervous system, causes the muscles to tense and the heart rate and respiratory rate to increase, and prepares the body to fight or to run away. This response-called the "fight or flight" response--underlies all responses to stress and that state of constant stress has been implicated in the development of a number of diseases.

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Noise pollution affects nearly every aspect of life and probably has damaging physical effects as well.

• Noise pollution impacts people's sleep.
• It can result in mood problems and adversely affect job performance.
• Several research studies suggest that noise can cause high blood pressure.
• Psychiatric diseases can be caused by noise.
• Noise affects us in another significant way: people exposed to noise feel a greater sense of frustration and annoyance than people whose environment is not as noisy.
• Noise pollution also causes fatigue, lack of concentration, irritability, tinnitus, and headache.

Effects of Noise Pollution on Physical Health

The most direct harmful effect of excessive noise is physical damage to the ear and temporary or permanent hearing loss often called a 'temporary threshold shift' (TIS). People suffering from this condition are unable to detect weak sounds. However, hearing ability is usually recovered within a month of exposure.

In Maharashtra, people living in close vicinity of Ganesh mandals that play blaring music for ten days of the Ganesh festival are usually known to suffer from this phenomenon. Permanent loss, usually called 'noise-induced permanent threshold shift' (NIPTS) represents a loss of hearing ability from which there is no recovery.

Below a sound level of 80 dB hearing loss does not occur at all. However, temporary effects are noticed at sound levels between 80 and 130 dB. About 50% of the people exposed to 95 dB sound levels at work will develop NIPTS (Noise Induced Permanent Threshold Shift) and most people exposed to more than 105 dB will experience permanent hearing loss to some degree. A sound level of 150 dB or more can physically rupture the human eardrum.

The degree of hearing loss depends on the duration as well as the intensity of the noise. For example, 1 hour of exposure to a 100 dB sound level can produce a TIS that may last for about one day. However, in factories with noisy machinery, workers are subjected to high sound l~vels for several hours a day. Exposure to 95 dB for 8 hours every day for over a period of 10 years may cause about 15 dB of NIPTS. In addition to hearing losses, excessive sound levels can cause harmful effects on the circulatory system by raising blood pressure and altering pulse rates.

Effects of noise pollution on mental health

Noise can also cause emotional or psychological effects such as irritability, anxiety, and stress. Lack of concentration and mental fatigue are significant health effects of noise. It has been observed that the performance of school children is poor in comprehension tasks when schools are situated in busy areas of a city and suffer from noise pollution.

As noise interferes with normal auditory communication, it may mask auditory warning signals and hence increases the rate of accidents, especially in industries. It can also lead to lowered worker efficiency and productivity and higher accident rates on the job.

Thus, noise is just more than a mere nuisance or annoyance. It definitely affects the quality of life. It is therefore important to ensure the mitigation or control of noise pollution.

Permitted noise levels *

Ambient Noise Levels dB Zone Day-time Night-time