On the transmission of sound through finite, closed shells: statistical energy analysis, modal coupling, and nonresonant transmission

An investigation of sound transmission into small enclosures considers the effects of acoustically induced coupling between shell modes. Using an integral equation approach, the transmission loss into a small rectangular box is computed and the level of cavity reactance examined. The noise reductions for a closed cylinder and a rectangular parallelepiped enclosure (with a single flexible panel) sitting in reverberant acoustic fields are computed and experimentally checked. The transmission by resonant and nonresonant shell modes is examined, especially In relation to the statistical energy analysis approach. The nature of the predominance of one type of transmission over the other Is considered in relation to shell and cavity configurations and structural damping levels. A technique is given for estimating the predominance of resonant or nonresonant modes as the basis for computations of sound transmission by flat panels and cylindrical shells in reverberant acoustic fields.