A Design Method for Minimizing the Sound Power Radiated from Plates by Adding Optimally Sized, Discrete Masses

Abstract

In this paper, a novel method for minimizing the sound power radiated from a structure is presented. The method involves placing strategically sized masses at specific locations on the structure’s surface. The minimization procedure modifies the shapes of the resonant modes of the structure in the frequency range of interest such that they are forced to radiate sound inefficiently. Because of this, they are referred to as “weak radiator” mode shapes. The method uses an optimization procedure that directly minimizes the radiated sound power from the surface of a plate in an infinite baffle. The procedure can be carried out for a single frequency or over a range of frequencies. Analytical sensitivities of sound power with respect to the design variables are developed and used in the optimization algorithm. Results on various test cases show sound power reductions of 10 dB or more even when several resonances are included in the frequency band. An acoustic intensity probe is used to experimentally verify the results for one test case. The experiment confirms the sound power reductions predicted by the optimization program.