Morphology influence on the acoustics of permeo-elastic media

This paper deals with the acoustics of permeo-elastic media. These media consist of a rigid porous skeleton on which flexible elastic films are fixed and interact with the fluid saturating the pores. They can correspond to foams, the thin membranes playing the role of films and the rigid structure being formed by the struts. The acoustics of permeo-elastic media can deviate from that of conventional porous media due to the fluid/film interaction at the pore scale. This introduces an elastic component in the energy that interacts with viscous and inertial effects. The actual behavior is established by the two-scale asymptotic homogenization method. It is shown that the film effects depend strongly on the pores and the film arrangement. Different wave propagation regimes are identified depending on the nature of the local flow. Consider- ing (i) fully connected, i.e., no pores are closed by the films, (ii) unconnected, i.e., all pores are closed, and (iii) partially connected, i.e., some pores are closed by the films, the study re- veals under which conditions the fluid-film interaction significantly influences the macroscopic acoustic behavior. Depending on the morphology, the permeability or compressibility (or both) can exhibit singularities or anomalous properties due to inner resonance or anti-resonance.