Acoustic wave transmission loss mechanisms in poroelastic media, modeling, and experiment.

Abstract

Among factors that determine acoustic wave transmission loss in poroelastic media are incident wave energy loss due to acoustic impedance mismatch, between pore fluid and solid frame, and their density ratio, in addition to frequency dependence of dissipation in viscous boundary layers of fluid-solid interface for compression and surface waves. Model for prediction of transmission loss mechanisms includes the use of dimensionless Prandtl and Strouhal numbers for momentum and heat transfers, respectively. Other mechanisms considered are transmission losses by resonant and wave localization in the pore spaces. Wave filtering by poroelastic media as well as transmission loss by mode conversion, scattering, diffraction, interference, absorption, and thermal conduction are considered. Mechanical and electrical models of low-pass, band-pass, and high-pass filters applied to poroelastic media lead to the type of parameters to be included in this model as a function of frequency and pore size. Experimental measurements to test the prediction on acoustic wave transmission loss in similar poroelastic media of constant uniform porosity, but of different thicknesses and pore sizes, are presented to test transmission loss as a function of pore size, media thickness, and acoustic wave frequency.