Sound absorption of a micro-perforated plate backed by a porous material under high sound excitation: measurement and prediction

Abstract

The sound absorption coefficient of perforated facings backed by porous materials is studied under high sound intensities in the absence of mean flow. The theoretical considerations are based on the equivalent fluid following the Johnson-Champoux-Allard approach and the use of the transfer matrix method. To take into account the high sound levels effects, the air flow resistivity of each layer is modified following the Forchheimer law. Two specimens of perforated plate are built and tested when backed by a polymeric foam and a fibrous material. A specific impedance tube setup is developed for the measurement of the surface acoustic impedance for sound pressure levels ranging from 90 dB to 150 dB at the surface of the perforated facing. To corroborate the validity of the presented method, two considerations are particularly depicted in the experimental results: first, the case where the perforated facing and the porous material are both directly backed by a rigid wall and the case where there is an air cavity between the porous material and the rigid wall. Good agreement is observed between the simulation and the experimental results.