This article presents a general mixed displacement-pressure formulation to analyze the dynamic behavior of anisotropic open porous materials. This formulation is obtained in the time domain without neglecting the acceleration terms related to the fluid phase of the porous medium. The derivation of the presented formulation uses Coussy’s description of porous materials. For isotropic media and harmonic motions, the developed general mixed formulation reduces to the common set of equations of motion used in acoustics which results directly from Biot’s equations. ©1997 American Institute of Physics.