Investigation of the sound transmission characteristics of sandwich panels

An analysis of the transmission of sound through sandwich panels (consisting of lightweight, flexible cores between relatively stiff skins) is presented. Previously given results for the free vibrations of such panels are analyzed and unified. Then a travelling-wave analysis is used to obtain impedances and transmission loss formulae. The comparison is relatively good, and confirmation of a symmetric coincidence effect is obtained. The numerical results indicate that this symmetric coincidence generally occurs at a much lower frequency then does antisymmetric (shear wave) coincidence. An optimization study is also presented to investigate the feasibility of an optimal design process for sandwich panels. Using a pattern search procedure, it is shown that the average transmission loss of a panel may be improved through optimization over a range of frequency.