Sound Propagation in Porous Materials Having a Rigid Frame

Abstract

In the preceding chapter, simple porous materials having cylindrical pores were studied. In the case of common porous materials, a modelling of the bulk modulus and the effective mass of the air, from the geometry of the frame, is generally impossible. This explains why the models that describe sound propagation in these materials are mostly phenomenological. A review of the models worked out before 1980 can be found in a work by Attenborough [1]. More recent studies have been performed by Lambert [2] and Attenborough [3]; and in the domain of acoustical materials with elastic frames by Desprez et al. [4], by the laboratories of acoustics of the universities of Le Mans and Leuven [5,6], and by Bolton and co-workers [7,8]. New developments, mainly put forth by Johnson et al. [9], are used in this chapter as the basis for new improvements in the description of sound propagation in porous materials. Measurements performed by Champoux [10,11] are presented to illustrate and verify the theoretical description.