Measuring permeability of porous materials via acoustic transmitted waves

A low frequency transmitted method is proposed for measuring the permeability of porous materials having a rigid frame. This parameter is important as one of several parameters required by acoustical theory to characterize porous materials like plastic foams and fibrous or granular materials. The proposed method is based on a temporal model of the direct and inverse scattering problem for the diffusion of transient low frequency waves in a homogeneous isotropic slab. This time domain model of wave propagation was initially introduced by the authors (Z.E.A Fellah et al, J. Acoust. Soc. Am., vol.107, p.683, 2000). The viscous losses of the medium are described by the model devised by Johnson et al (Fluid. Mech., vol.176, p.379-402, 1987). Reflection and transmission scattering operators for a slab of porous material are derived from the responses of the medium to an incident acoustic pulse. The permeability is determined from the expressions of these operators. Experimental and numerical validation results of this method are presented. This method has the advantage of being simple, rapid and efficient.