ACOUSTIC PERFORMANCE OF COATINGS COMPRISING PERIODIC VOIDS AND STEEL INCLUSIONS IN RUBBER

摘要

The acoustic performance of coatings comprising both a periodic layer of voids and a periodic layer of steel cylinders in an elastic medium with a steel backing is analytically and numerically investigated. The analytical model is based on effective medium approximation theory whereby each layer of scatterers is modelled as a homogeneous medium. The numerical model is based on the finite element method. Peaks of high sound absorption are attributed to Fabry-Perot resonance associated with the presence of the voids as well as dipole resonance of the steel scatterers in the elastic medium. The performance of acoustic coatings comprising a layer of voids and a layer of steel inclusions are compared with those comprising two layers of voids or two layers of steel inclusions. The coating comprising a layer of steel inclusions followed by a layer of voids in the direction of sound propagation is shown to have the best broadband sound absorption performance.