Key words: Fluid-structure, finite element, modal reduction, double panel, sound transmission.

Abstract: This paper presents a finite element model for sound transmission analysis through a double panel inserted in an infinite baffle. The proposed model is derived from a multi-field variational principle involving structural displacement and acoustic pressure inside the fluid cavity. To solve the vibro-acoustic problem, the plate displacements are expanded as a modal summation of the plate's eigenfunctions in vacuo. Similarly, the cavity pressure is expanded as a summation of the modes of the cavity with rigid boundaries. Then, an appropriate reduced-order model is introduced. The structure is excited by a plane wave at the source side. The radiated sound power is calculated by means of a discrete solution of the Rayleigh Integral. Fluid loading is neglected. An example of the normal
sound transmission loss of a double aluminum panel is shown. This example illustrates the accuracy and the versatility of the proposed reduced order model, especially in terms of prediction of sound transmission.