Numerical prediction of noise transmission loss through viscoelastically damped sandwich plates

This study describes the numerical prediction of noise transmission loss (TL) through sandwich plates subjected to an acoustic plane wave or a diffuse sound field excitation. The sandwich plate considered is made up of a viscoelastic core sandwiched between two elastic faces. The model presented is based on a finite element formulation for the sandwich plate coupled to a boundary element method for the acoustic medium. The plate formulation is derived from Kirchhoff's theory for the elastic faces and Mindlin's theory for the core. The strain and kinetic energies of the sandwich plates are written in terms of the mean and relative in-plane displacements of the faces and the transverse deflection of the plate. The diffuse sound field is modeled as a superposition of uncorrelated plane waves with equal amplitude. The vibroacoustic equations obtained are discretized using a triangular finite element. The accuracy of the present model is demonstrated by comparing it with analytical and experimental results available in the literature. New results on laminated glass showing the effects of temperature on the TL are presented.