19th Asia-Pacific Vibration Conference (APVC2021)

A microperforated panel (MPP) absorber has been presented as a substitute for traditional and common conventional (Fibrous and Porous) sound-absorbing materials due to their low energy dissipation and poor absorption performance of low-frequency sound. This paper examines parametric study on the low-frequency sound absorption and wider absorption bandwidth characteristics of a double-layer multiple parallel-arranged inhomogeneous microperforated panel (DL-iMPP) absorbers. The theoretical formula for calculating the absorption coefficient under normal incident sound is established based on an electrical equivalent circuit model (ECM). Theoretical and parametric study based on ECM is performed on the MATLAB software, and the predicted results are obtained. The results show that by varying and adjusting the thickness, perforation size, perforation ratio, width, and height of back-cavity depths, the proposed model can produce wider absorption bandwidth of 175~430 Hz in the low-frequency region with a decent average absorption coefficient of more than 80% (α = 0.83) compared to the existing studies. In addition, by increasing the depth of the cavity behind a sub-MPP with large diameter holes and a small perforation ratio, the bandwidth can be improved to a lower frequency. Samples were made using Liquid Crystal Display (LCD) technology for the experimental validation. The MATLAB simulation-based predicted results are validated through square impedance tube-based experiments.