Sound radiation from a finite perforated panel set in a rigid baffle: A fully coupled analysis

Abstract

A fully coupled formulation is presented for sound radiation from a finite flexible perforated panel set in an infinite rigid unperforated baffle. The panel is excited by a point harmonic force and radiates sound into the acoustic medium on both sides of the baffle. Prior to coupling with the fluid, the change in the inertial and stiffness properties of the panel due to perforations and their effect on the in vacuo natural frequencies and mode shapes are accounted for using the receptance method. The coupled acoustic and structural equations are formulated using the 2-D wavenumber transforms. Since the formulation is in terms of the panel velocity, a certain square root singularity that typically appears in the denominator is avoided. The self- and inter-modal coupling coefficients are evaluated either analytically or numerically. The radiated power, panel mean quadratic velocity and radiation efficiency plots are obtained for different perforation ratios for both center and off-center excitations. At first, our formulation is validated against an unperforated case using a study available in the literature. Next, for our perforated panel case, we assume that both the half-spaces are filled with the acoustic fluid. It is observed that the radiation efficiency decreases with the increase in the perforation ratio, irrespective of the surrounding acoustic medium. However, for the water-loaded panel, the radiation efficiency is found to be lower than when the panel is immersed in air. It is found that for a light fluid like air, a one-way coupled formulation is adequate. The natural frequencies of a water-loaded perforated panel are also presented. It is found that for a given mode, the natural frequency increases with increase in the perforation ratio.