Sound absorption of acoustic resonant absorbers with rough oblique perforations

Abstract

Micro-perforated panel sound absorbers are widely used in the field of noise reduction due to their good sound absorption performance. For micro-perforated panel, the acoustic impedance characteristics of the perforation hole play an extremely important role in the sound absorption performance. Here, the acoustic metamaterial in the form of a perforated panel with rough oblique holes is proposed for low-frequency sound absorption. By introducing surface roughness, the acoustic performance of the oblique perforation holes can be adjusted, and the low-frequency sound absorption performance of the perforated panel sound absorber is improved. The theoretical prediction of sound performance has been verified by finite element simulation, and a good consistency has been achieved. The results show that the introduction of surface roughness effectively reduces the resonant frequency and increases the value of sound absorption peak. The introduction of surface roughness and oblique configuration can provide additional acoustic resistance and reactance for impedance matching with air without increasing the thickness of the structure, resulting in more effective low-frequency sound absorption. Physically, the surface roughness causes the periodic concentration effect of the fluid vibration in the hole, which increases the viscosity loss and improves the sound absorption performance of the sound absorber. The theoretical and the numerical models, as well as the low-frequency perfect sound absorption performance (α>0.99) of the proposed metamaterial, are validated by experimental measurements. This work is of great significance to the application of perforated panel absorbers in low-frequency sound absorption.