Biot Theory of Sound Propagation in Porous Materials Having an Elastic Frame

Abstract

As shown previously, precise predictions for sound propagation in ordinary rigid framed porous materials are generally difficult to obtain, due to the complexity of the frame geometries. For the case of materials having an elastic frame, the description of sound propagation is more complicated. A general model exists, the homogenization theory [1-7], that links the macroscopic and the microscopic descriptions of sound propagation. This theory is beyond the scope of this book. A more phenomenological and easily handled model is the Biot theory [8,9]. For the porous materials having a flow resistivity smaller than 50 000 Nm-4 s, the two theories are compatible at least at frequencies higher than 100 Hz (see Section 1 of Ref. [6]).