Tunneling effect on the sound transmission loss of a flat structure coupled with a porous material

Abstract

It is well known that when measuring Sound Transmission Loss (STL) in a laboratory, among all test conditions, the location of a specimen in an aperture affects the results, due to the tunneling effect. Previous studies have considered this effect for flat single panels and double walls but the case of a panel with attached sound package seems to have received very little attention. This paper deals with the application of a modal approach to study the STL of a rectangular plate coupled with a porous material located inside a tunnel. The sound absorbing material is supposed to be either described by a modal approach or a transfer matrix calculated using a Transfer Matrix Method which relates interstitial pressure and total normal stress on both sides of the material. The model is validated by comparison with Finite Element/Boundary Element computations. Numerical results are shown to illustrate the validity of the proposed full modal and hybrid modal-TMM methodologies and their use to investigate the niche effect in presence of a sound absorbing material. © 2013 Acoustical Society of America.