Text: The general expression for the velocity of a compressional wave in a deformable medium is the first equation to the left where dp is the change in pressure accompanying the change dp in density. Since the compressions and rarefactions accompanying the propagation of sound through a gas are adiabatic, the relation between pressure p and volume V is the well-known one pVg = constant (g being the ration cp/cv) of specific heat at constant pressure to that at consant volume), and the first equation becomes the second for a gas.

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