Waves and Oscillations - Wave Motion : Displacement Wave Versus Pressure Wave

A longitudinal mechanical wave can be described either in terms of the longitudinal displacement suffered by the particles of the medium (called displacement-wave) or in terms of the excess pressure generated due to compression and rarefaction (called pressure-wave). Actually a longitudinal mechanical wave has these two representations. It is found that the phase difference between these two waves is 90-degree.Therefore displacement is maximum when pressure is minimum and vice-versa. As sound sensors,e.g.,human ears,or mike or electronic detectors etc give response to pressure changes,hence pressure representation of sound wave is preferred over displacement representation.