Noise is probably the most frequently forgotten of the environmental pollutants, yet its effects can be many and far-reaching.
Sources of Noise Pollution
The sources of noise pollution vary. In some places noise from construction projects predominates, while in others it is vehicular traffic or noise from airports. Other sources include the noise in occupational settings or even the noise of simultaneous conversations. It also seems from a number of studies that intermittent noise is more of a problem than noise of a similar intensity which is constant.
Effects of Noise Pollution
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.
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.
Noise Pollution
Noise may not seem as harmful as the contamination of air or water, but it is a pollution problem that affects human health and can contribute to a general deterioration of environmental quality.
Noise is undesirable and unwanted sound. Not all sound is noise. What may be considered as music to one person may be noise to another! It is not a substance that can accumulate in the environment like most other pollutants. Sound is measured in a unit called the 'decibel' (dB).
The differences between sound and noise is often subjective and a matter of personal opinion. There are, however, some very harmful effects caused by exposure to high sound levels. These effects can range in severity from being extremely annoying to being extremely painful and hazardous.
Decibel levels of common sounds
dB Environmental Condition
0 Threshold of hearing
10 Rustle of leaves
20 Broadcasting studio
30 Bedroom at night
40 Library
50 Quiet office
60 Conversational speech (at 1m)
70 Average radio
74 Light traffic noise
90 Subway train
100 Symphony orchestra
110 Rock band
120 Aircraft takeoff
146 Threshold of pain
Effects of Noise Pollution on Physical Health
The most direct harmful effect of excessive noise is physical damage to the ear and the 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 everyday 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
Silent Zone 50 40
Residential Zone 55 45
Commercial Zone 65 55
Industrial Zone 70 70
A standard safe time limit has been set for exposure to various noise levels. Beyond this 'safe' time continuing exposure over a period of a year will lead to hearing loss.
Duration dB
8 hours 90
4 hours 93
2 hours 96
1 hours 99
30 minutes 102
15 minutes 105
7 minutes 108
4 minutes 111
2 minutes 114
1 minutes 117
30 seconds 120
Instantaneous
rupture
of membrane 150
*The permissible figures above can be different for each city or state as prescribed by the state Noise Pollution Board.
Compiled By Dr. Himanshu Kumar, Mentor, Mini Theaters India, INDIA & UAE.