Enhanced wideband low-frequency sound absorption of a single-layer multiple parallel-arranged inhomogeneous microperforated panel absorber

A single layer of four parallel-arranged inhomogeneous microperforated panels (iMPP) absorber is proposed to achieve low-frequency sound absorption and wider frequency bandwidth. The hole diameter of the four parallel-arranged iMPP is set to be equal to or less than 1 mm. The theoretical formula for calculating the absorption coefficient under normal incident sound is established based on an electrical equivalent circuit model (ECM). The parametric study has been performed on the MATLAB software, and the expected results are obtained. The results indicate that the proposed model can produce a wider absorption bandwidth of 195–455 Hz in the low-frequency region with an average absorption coefficient of more than 90% (α = 0.91). To achieve the desired effect, the absorption coefficient and the bandwidth can be tuned by adjusting the aperture size, perforation ratio, thickness of iMPP with depth and width of the back cavity. Also, it is found that iMPP can produce wider bandgaps with good absorption peaks in the low-frequency region by designing sub-MPP of smaller hole diameter, large perforation ratio, and with large cavity depths and the sub-MPP of large hole diameter, small perforation ratio, and with short cavity depths. The finite element method has been employed on COMSOL Multiphysics 5.5a to simulate the acoustic absorption performance of the model and compared with the ECM-based predicted and square impedance tube-based experimental results. Compared with other homogeneous MPPs of different arrangements, this absorber provides exceptional absorption performance in a low-frequency range due to its lightweight structure, and convenient manufacturing availability, this enhanced form of iMPP absorber has great potential in acoustics and noise control applications.