Experimental measurement of the porosity and the viscous tortuosity of rigid porous material in low frequency

Abstract

In this paper, an acoustic method is presented for measuring the porosity and the viscous tortuosity of air-saturatedporous materials at low frequencies. The proposed method is based on a temporal model of the direct and inverse problem for the reflection of low-frequency waves by homogeneous isotropic slab of porous material having a rigid frame. Reflected coefficient for a slab of porous material is derived from the responses of the medium to an incident acoustic pulse where a simple relation between flow resistivity, porosity, viscous tortuosity and the reflected waves is obtained. A numerical method and efficient tool for the estimation of the porosity and the viscous tortuosity are presented and discussed.