A wave equation for the propagation of sound in suspensions or emulsions has been formulated from the simple considerations of mass and momentum balances on a sufficiently small homogeneous and compressible volume element of the suspension in the sound field. The induced masses of the non‐neutrally buoyant oscillating particles and the adiabatic compressibilities of suspension components have been shown to modify the equations of continuity and momentum and thereby the wave equation, with respect to those equations for the single‐phase suspending fluid. A formula for the velocity of sound in suspensions has been deduced, which agrees with that derived from the scattering theory.