Sound is a kind of wave motion which is transmitted in the form of pressure wave. Such waves are received by hearing apparatus of animals and men in the form of electrical impulses. These electrical impulses are covered to brain which enables them to hear. Sound waves are generated in a number of ways. It has been observed that the intensity of sound waves diminishes with the increase in the distance of the objects which come in the way of waves.

Sound is a normal feature of our life. It is also a major means of communication.

Measurement of Sound :

The intensity of sound is measured on a scale called decibel scale or db scale. It measures the loudness of sound in terms or relative units of energy or power on a logarithm scale. The scale starts from 0 db and is considered as threshold of hearing which the human can hear. A sound of 10 db is ten times louder than 0 (zero) db and a sound of 20 db is 10 x 10 times louder and likewise a sound of 30 db is 10 x 10 x 10 times louder.

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Effects of Noise Pollution :

Unwanted sound is known as noise, which causes discomfort. It is also called as a wrong sound in the wrong place at the wrong time. The definition of noise does not allow us to discriminate between pleasurable sound and noise. A given sound may be considered music by some and noise by others. The most significant attribute to noise is its loudness. Loudness is taken as a criterion for noise pollution. Noise is a physical form of pollution. It does not persistent harm to life supporting systems.