Finite element modeling of isotropic elastic porous materials coupled with acoustical finite elements

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Abstract
In this paper the development of a two-dimensional elastic-absorption finite element model of isotropic elastic porous noise control materials is described. A method for coupling elastic-absorption finite elements with conventional acoustic finite elements is also presented for the cases when the interface between the adjacent air space and the foam is either unfaced or sealed by a membrane. The accuracy of the acoustic/elastic-absorption model has been verified by comparing its predictions with analytical solutions for the case of wave propagation in a foam-filled waveguide. Further, the finite element model has been used to investigate the effect of edge constraints on the surface normal impedance of a foam sample in a standing-wave tube. As expected, edge constraints were found to stiffen the foam acoustically at low frequencies.