  The equations of motion in a macroscopically inhomogeneous porous medium
saturated by a fluid are derived. As a first verification of the validity of
these equations, a two-layer rigid frame porous system considered as one single
porous layer with a sudden change in physical properties is studied. A simple
wave equation is derived and solved for this system. The reflection and
transmission coefficients are calculated numerically using a wave
splitting-Green's function approach (WS-GF). The reflected and transmitted wave
time histories are also simulated. Experimental results obtained for materials
saturated by air are compared to the results given by this approach and to
those of the classical transfer matrix method (TMM).
