Acoustic Absorption of Multi-Layer Structure Composed of Porous Layers Based on Biot's Model and Transfer Matrix Method

This article presents an approach of modelling the surface impedance and absorption coefficient of multi-layer structure composed of porous materials placed against a rigid wall. The Biot's model is used to calculate the complex wave numbers of the two compressional waves propagating in porous materials at normal incidence and the surface impedances of multi-layer structures are predicted by the transfer matrix method (TMM). The resonance effects of structures composed of three layers of different porous materials are studied and the arrangement of each layer and the influence of their thicknesses are also discussed.