Acoustic absorption of macro-perforated porous materials

The paper discusses the absorption of non-homogeneous thin macro-porous materials. In particular, the acoustic absorption performance of three-dimensional (3-D) porous media made up from thin porous patches, with different acoustic properties, is investigated using a numerical model. The presented model considers the configuration wherein the material is bonded onto the hard-walled termination of a semi-infinite rectangular waveguide. It couples a finite element description for the porous material to a modal description in the waveguide and uses a power balance approach to accurately quantify the absorption performance of the material. Experimental results are presented to validate the model in the special case of a macro-perforated porous material. Using this model a parameter study is presented. It is shown that absorption may be increased at low frequency by using non-homogeneous patch-works. (C) 2001 Academic Press.