Sonic Crystals for Highway Noise Reduction

Sonic crystals are noise barriers which have come to picture since the last two decades for their sound attenuation properties. They consist of sound scatterers arranged periodically inside a host material. The scatterers have high impedance and are put in a fluid of low impedance. Sound attenuation takes place due to multiple scattering of sound waves by the rigid sound scatterers, within particular frequency bands known as Band Gaps. In this paper, a finite element study has been performed on a 2-D sonic crystal having circular scatterers arranged in square pattern. The scatterers are assumed to be sound hard, which imposes that the normal velocity and normal acceleration at their boundary are zero and the arrangement is periodic which is because of the cyclic symmetry of the structure. Relevant boundary conditions have been incorporated into the design which aims in determining the Band Gaps and the corresponding transmission losses through the sonic crystal. Results of eigenfrequency and frequency response analysis of the scatterers are done using a commercial finite element software, COMSOL Multiphysics are presented in this paper.