Porous layer impedance applied to a moving wall: Application to the radiation of a covered piston

International audienceModelling a porous layer mounted on a vibrating wall by mean of an acoustic impedance is investigated in this paper. It is shown that the use of the surface impedance usually measured with the impedance tube method can provide erroneous estimation of the acoustic pressure radiated by the coated structure. The paper focuses on the derivation of an impedance, denoted the ”transfer impedance”, which describes accurately the dynamic movement of the porous layer. Biot's theory is used in the model to account for deformations in the thickness of the layer. Experimental validation is performed using a circular piston covered by a foam or a brous layer and radiating in a innite halfspace. The radiation model including the transfer impedance shows good agreement with experimental data