404 Sound Decreasing Effects of Sound Absorbing Material Structures Installed on the Vibrating Rigid Surface

Abstract

Sound decreasing effects of sound absorbing material structures installed on the moving rigid surface were verified experimentally for both the stationary and the nonstationary cases by using the one-dimensional acoustic tube. The decreasing effects were evaluated in the frequency spectrum domain by taking the discrete Fourier Transform for the nonstationary case, and almost 70% sound pressure decreasing effect was observed at the maximum in the range of 0.5〜3kHz for the hard porous or fiber alminum sound absorbing material structures with back air space. Then two kinds of quantitative estimation methods of those decreasing effects were examined.