The Damping of Panels by Thick Layers of Elastic Porous Media

In this paper a technique is presented for calculating the response of a panel to a line force input when loaded by both a finite‐depth layer of elastic porous material and a heavy fluid. Damping theories normally require that an attached damping layer be thin compared to the flexural wavelength in the base panel. Here this requirement is avoided by allowing explicitly for wave propagation within the damping layer. Specifically, the porous damping layer is modeled using a theory derived by Biot that allows for the existence of two dilatational waves and a transverse wave. Conditions required to couple the porous medium to the panel and an adjacent fluid will be discussed. A formal solution for the plate response may be obtained easily in the wavenumber domain. Although it is not possible to obtain the spatial response analytically in this instance, it will be shown that under practical circumstances the required inversion integral may be evaluated efficiently and “exactly” by using the fast Fourier transform algorithm. Results will be given illustrating the damping potential of thick layers of porous materials

Sound Transmission through Stiffened Double-Panel Structures Lined with Elastic Porous Materials

This paper presents transmission loss prediction models for a periodically stiffened panel and and stiffened double panel structures using the periodic structure theory. The inter-panel cavity in the double-panels structures can be modelled as being separated by an airspace or filled with an elastic porous layer in various configurations. The acoustic behavior of the elastic porous layer is described by a theory capable of accounting fully for multi-dimensional wave propagation in such materials. The predicted transmission loss of a single stiffened panel is compared with the measured data