An experimental study for the penetration of sound into a rigid porous medium

Abstract

In a recent study, a new analytic solution for computing the penetration of airborne sound into a rigid porous ground has been derived. Modeling the lower medium as a modified fluid, a simple analytic solution can be obtained that can be cast in a form analogous to the Weyl‐van der Pol formula for the sound field in the upper medium. The current study is devoted to an experimental validation of the analytical model. A layer of glass beads is used in the experimental study for modeling the rigid porous ground. To test the analytical formulation, measurements of excess attenuation spectra above and within the layer of glass beads were conducted. The impedance, propagation constant, and the index of refraction of the glass bead aggregate were deduced from the excess attenuation spectra. The experimental results are compared with other methods for finding the propagation of the rigid porous medium. The proposed method suggests a new way of finding the propagation constant and the index of refraction of a rigid porous medium.