Time-domain equations for sound propagation in rigid-frame porous media (L)

A general set of time-domain equations describing linear sound propagation in a rigid-frame, gas-saturated porous medium is derived. The equations, which are valid for all frequencies, are based on a relaxational model for the viscous and thermal diffusion processes occuring in the pores. The dissipative terms in the equations involve convolutions of the acoustic fields with the impulse response of the medium. It is shown that the equations reduce to previously known results in the limits of low and high frequencies. Alternative time-domain equations are also derived based on a Padé approximation.