Use of Type II sequence diffusers for the purpose of improving noise barrier effectiveness

Abstract

The Type II Luke sequence diffusers have been known to redirect sound energy and act as a beam steerer at certain frequencies. If the incident sound from the top-edge of a noise barrier can be redirected away from the shadow zone by installing such a device, the insertion loss of the noise barrier can be significantly improved. Numerical analysis revealed that the use of multiple periods of Luke sequence diffusers as reflection phase gratings has potential to improve nose barrier effectiveness even more than using a single diffuser on the top-edge. Compared to a rigid T-barrier, improvement in overall A-weighted insertion loss of 8dBA was achieved by installing sound diffusers designed on the Type II luke sequence on the top-edge of the noise barrier.