Numerical Analysis of Sound Transmission to Modeled Walls

Abstract

This paper provides the results of a numerical analysis on sound transmission to modeled solid and hollow walls in order to investigate the acoustic characteristic of a honeycomb sandwich structure. The finite difference time domain (FDTD) method is used in this study because it is possible to solve both sound wave propagation in gas and elastic wave propagation in solid simultaneously. Two types of simple two-dimensional wall model are considered in order to compare the characteristics of sound transmission by an incident plane wave. One is an isotropic solid wall and the other is a hollow wall which models a honeycomb sandwich structure. In the case of isotropic solid wall calculations, the sound transmission loss obtained by FDTD analysis has a good agreement with that of the mass law, when the wall model is sufficiently thin compared with the wave length of incident wave. On the other hand, the arch-shaped transmission wave is observed in the case of hollow model calculation, which is totally different from that of simple solid wall model. In addition, it is found that the mode excitation in the inner fluid region of hollow wall model occurs according to the frequency of incident wave, and that a beat appears in the transmission wave.