A thin double-layer multiple parallel-arranged inhomogeneous microperforated panel absorber for wideband low-frequency sound absorption

We propose a thin double-layer multiple parallel-arranged inhomogeneous microperforated panel (MPP) absorber in which the perfect low-frequency (i.e., 100-500 Hz) sound absorption with wider bandwidth is achieved with deep subwavelength of thickness (100 mm). This unique thin structure absorber consists of a double-layer MPP formed by four single parallel-arranged inhomogeneous MPPs with different hole sizes, perforation ratio and air-cavity depth at the back. Theoretical study based on electrical equivalent circuit model (ECM) is performed on the MATLAB, and the predicted results are obtained. The results show that compared to the existing studies, the proposed model can produce wider absorption bandwidth of 175 similar to 430 Hz in the low-frequency region with a decent average absorption coefficient of more than 80% (alpha = 0.83). FEM is employed on COMSOL Multiphysics 5.5a to simulate the acoustic absorption performance of the model and compared with the ECM's predicted and square impedance tube-based experimental results. The results are fairly well aligned with the ECM's predicted and square impedance tube-based experimental results. In addition, by carefully designing the parameters of current model the bandwidth can be further improved toward a lower frequency. Such kind of absorber could be used in wide applications in noise control engineering owing to its excellent absorption performance, relatively broad bandwidth, lightweight structure and convenient manufacturing availability.

Automated summary

A new type of absorber consisting of multiple parallel-arranged inhomogeneous microperforated panels (MPPs) is proposed to achieve wideband low-frequency sound absorption. The theoretical study and simulation results show that this absorber can produce a wider absorption bandwidth with a high absorption coefficient in the low-frequency region. Furthermore, the performance of the absorber can be further improved through optimization.