Vibro-acoustic behavior of a cavity backed by a plate coated with a meso-heterogeneous porous material

The acoustic absorption performance of heterogeneous materials made up from a combination of thin porous patches, with different acoustic properties has been investigated recently by the authors. It has been shown that absorption could be significantly increased in the case of properly designed macroperforated wools in a large frequency band. This paper concentrates on the damping induced by a porous material containing embedded meso-heterogeneities. This meso-heterogeneous porous material is made up of a porous substrate containing solid inclusions or air cavities. It is attached to the inner face of a panel radiating inside a cavity. The panel is either excited mechanically or acoustically using an oblique incidence plane wave. The numerical model is based on a finite element formulation for the different material components. The coupling between the inclusions (solid or acoustic) and the porous patches is accounted for naturally through the use of an appropriate mixed pressure-displacement formulation of Biot's poroelasticity equations. Numerical and experimental results are presented to show the influence of heterogeneities on the damping in the system.