Optimization of the Acoustic Properties of a Multilayer Sound Absorber by using the Genetic Algorithm

In this paper, the acoustic properties of multilayer sound absorbers were optimized by using the genetic algorithm (GA). The multilayer sound absorber was combined with a porous material layer attached behind a micro-perforated panel absorber (MPPA) layer, and backed by an airgap layer. The analytical model was constructed by utilizing the Transfer Matrix Method (TMM). In this method, Maa’s formula and the Johnson-Champoux-Allard (JCA) equivalent fluid model were used to describe the MPPA layer and the porous material layer, respectively. The sound absorption coefficient (SAC) of the multilayer sound absorber was measured by using the two-microphone impedance tube method. A comparison was made between the measurement data and the calculation results to verify the usefulness of the analytical approximation. Furthermore, the GA was used to optimize the multilayer sound absorber so that an optimal combination of the structural parameters could be obtained. The results have shown that the optimized multilayer sound absorber has a wider absorption bandwidth and a higher absorption coefficient in the frequency range from 100 Hz to 1600 Hz, and that the GA was effective for optimizing the sound absorption coefficient of the multilayer sound absorber. Finally, the effect of the design parameters, such as the thickness of each layer, and the perforation ratio of the MPPA layer on the sound absorption coefficient is discussed.