Define the Nature of Sound

This section is a recapitulation of what you have learnt in school. You would recall that sound waves consist of the longitudinal waves of alternate compression and rarefaction. Areas of compression have a higher pressure and density of air molecules than the area of rarefaction.

The waveform propagates itself for long distance because of the influence, which the areas of compression or rarefaction have on the neighbouring areas. Thus, it is only the waveform that is transmitted and not the air molecules. The velocity of sound depends on the medium through which it is transmitted. In air, the velocity is about 340 m/sec. The loudness of a sound is related to the amplitude of pressure waves and the pitch to their frequency. Let us understand what we mean by the term 'amplitude'.