A coupled boundary element (BEM) - finite element (FEM) approach is presented to accurately model structure-acoustic interaction systems. The coupled BEM/FEM analysis is compared with existing classical, modal approximation, and experimental solutions for isotropic panels, (Brass, Aluminum), under simply supported and clamped boundary conditions. These comparisons show that the coupled procedure gives accurate and reliable solutions to complex problems.Composite panels are then analyzed. Various composite layups are utilized for the same plate/cavity system to understand the effects of the composite materials. Transmission loss data for composite and isotropic panels are analyzed. As expected, the composite panels give lower transmission loss results compared with the isotropic panels. A lamination study is also provided to show the orientation angle effect on overall transmission loss.