Acoustic performance of periodic composite materials

Sonic crystals are finite arrays of periodically arranged scatterers, for which very low noise transmission occurs in certain frequency bands known as stop bands or band gaps. The location of these band gaps can be tuned by changing the spacing between adjacent scatterers in the periodic array. Sonic crystals are receiving recent interest for practical applications ranging from vibro-absorbing coatings for attenuation of structure-borne noise to acoustic barriers for environmental noise reduction. In this work, analytical and numerical models of a simple sonic crystal comprising periodically arranged inclusions in a host medium are developed. The analytical model is based on the effective medium approximation method, whereby the composite material is modelled as a homogeneous viscoelastic material, determined by the volume fraction of the inclusions in the composite. A finite element model of the sonic crystal using the commercial software COMSOL Multiphysics is also developed. The acoustic performance of the sonic crystal array obtained analytically and numerically is compared.