Inhomogeneous Biot waves in layered media

Abstract

A description, using transfer matrices, is given of the propagation of the three inhomogeneous Biot waves in layered porous media. This is applied to predict the surface impedance of porous layered materials at oblique incidence, and an example is presented.

Inhomogeneous Waves in Anisotropic Porous Layer Overlying Solid Bedrock

“…For the verification of transfer matrix determined in this paper, justification of numerical computation and to study the effects of transversely isotropy, the calculations have been done for the case when both the porous layers are isotropic, i.e., by setting the values of e; d and g to be zero. The results in this situation should be in agreement with those obtained by Allard et al [7] and these are found so. The transverse isotropy of layers is found to increase both real and imaginary parts of the surface impedance.…”

“…Here, two layers of plastic foam are modelled as transversely isotropic porous layered medium. We adopted the values of physical parameters for the two layers of foam as given by Allard et al [7] and determined the values of the material coefficients used in this paper, by using the relations mentioned therein. The values of physical parameters for transversely isotropic porous medium can be obtained from those for isotropic one by the relations Using these values of material coefficients, the surface impedance is computed in the high-frequency range.…”

“…Plane wave propagation in layered porous media at normal as well as oblique incidence is studied by Allard et al [6,7]. Lauriks et al [8] used the method of transfer matrix in the study of plane wave propagation in layered media.…”

Recent Advances in the Sound Insulation Properties of Bio-based Materials

“…Thus, there should be enough pores in the material for the sound to pass through and to get dampened. The porosity of a porous material is defined as the ratio of the volume of the voids in the material to its total volume (Allard et al 1989). Variable densities may result in different behavior of noise reduction since the density has great influence on the porosity of fibrous assemblies.…”

“…(Chin et al 1985) 1989 A simpler model was derived with transfer matrices which described the sinusoidal wave propagation in a layered porous material. (Allard et al 1989) 1993 A five parameters model, which yields the noise absorption coefficients of fiber webs as a function of their thickness and porosity. (Allard, Herzog et al 1993) 1993 Studied the wave propagation in an anisotropic layered fluid saturated porous medium backed by an impervious surface at oblique incidence (Sun et al 1993).…”