Sound and vibration analysis of a nonlinear panel absorber mounted on an enclosure panel using the multi-level residue harmonic balance method

A thin metal panel absorber is usually mounted on an enclosure panel to enhance its acoustic absorption performance because of its light weight and good durability. Few studies have investigated the sound radiation from an enclosure panel mounted with a nonlinear panel absorber, although there have been many on nonlinear plates, linear structural-acoustic coupling problems, the sound absorption of various panel absorbers, and sound radiation from vibrating structures. In this paper, a multi-structural acoustic modal formulation is derived from two coupled partial differential equations representing the sound radiation from an enclosure panel subject to the acoustic pressure induced by a nonlinearly vibrating panel absorber. The results obtained from the multi-level residue harmonic balance method are in reasonable agreement with those obtained from a numerical integration method. In a parametric study, the panel displacement amplitude converged with an increasing number of modes. The effects of excitation level, damping, aspect ratio, cavity depth, and resonant frequency ratio are examined here. It can be concluded from some of the numerical results that the nonlinear resonances of a panel absorber can increase sound radiation if they are strongly coupled with the linear resonance of the enclosure panel. In other words, the panel absorber deteriorates the enclosure panel's sound insulation performance.