Measurement of the nonlinear behavior of acoustical rigid porous materials

Abstract

The measurement of the flow resistivity of porous materials shows that two types of behavior can be observed, depending on the value of a Reynolds number based on the porous material microgeometry. For Reynolds numbers (Re) smaller than a critical Reynolds number, the increase of the resistivity is quadratic in Re. For Re larger than this value the increase is linear in Re (Forchheimer’s law). A comparison between acoustic measurements and an equivalent fluid model shows that the main effect of high sound level on sound propagation through rigid porous materials is the variation of the flow resistivity.