Directivity Based Noise Control for an Obliquely Incident Transmission Problem

The objective of the present work is to improve the transmission loss offered by a barrier separating two acoustic spaces. The barrier is subjected to a low frequency obliquely incident acoustic pressure over one side. A novel concept of achieving this is proposed through addition of point mass at the optimal location over the barrier surface. This allows for a local control of the transmitted noise at the target location through a control on the directivity pattern. It is noted that for some target directions high reduction in sound pressure is possible as compared to the unloaded plate whereas, for other target directions only marginal reduction in sound pressure is achievable by point mass attachment. This is in contrast to the normal incidence transmission problem where it is equally possible to achieve noise control in any direction viz. normal, tangential and oblique direction to the plate by attachment of a point mass at the optimal location on plate.