Optimization of double-layered micro-perforated panels with vibro-acoustic effect

Abstract

A vibro-acoustic effect, in which the classical plate equation is coupled to the acoustic wave equation, was utilised to optimally tune a double-layered flexible micro-perforated panel (MPP), to achieve higher sound absorption coefficient and wider frequency band. The first nine modes considered in the present modelling study were obtained by using the finite element analysis. Results of the vibro-acoustic model, applied to a single layer MPP, were found to be in a good agreement with other published results; thus, the model was used to develop the equivalent electro-acoustical circuit of a double-layered MPP sound absorber. The simulated annealing optimization technique was used to obtain the optimal design parameters of the MPP sound absorber that were needed to achieve the maximal averaged sound absorption coefficient for the frequency band 200–1,000 Hz. The optimized double-layered MPP sound absorber improved the sound absorption coefficient by 8.88–12.52 % compared with the model without the vibro-acoustic effect. Mode (1, 1) was found to dominate the sound absorption performance compared to the other nine mode shapes that were considered in the present study. The effects of configuration, thickness, damping ratio, and boundary condition of the MPP on the sound absorption coefficient were also investigated.