Sound absorption coefficient of a porous material covered with a low open area perforated plate under high sound excitation

International audience; The sound absorption coefficient of porous materials covered with low open area perforated plate 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, prediction and measurements are compared for the case where the perforated facing and the porous material are both directly backed by a rigid wall. Good agreement is observed between the simulation and the experimental result.