Sound propagation and absorption

As all waves, sound waves are characterised by speed, frequency and amplitude. 

Sound speed gives the magnitude of the sound velocity vector it is expressed in units of m/s and symbolised by the symbol u (or sometimes by o or c). 

Sound frequency is the reciprocal of the period of the sound wave. It is denoted by the symbol v and expressed in cycles per second with the Hertz (s 1) as unit. Also the angular frequency is used the latter is symbolised by co, which is identical with 2nv. 

In fluid media, such as gases or liquids and melts, which have no rigidity, only longitudinal waves can occur. In media that have rigidity but are incompressible, only transverse waves can occur. 

So the Poisson ratio plays an important part in sound propagation. 

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