Modular low-frequency broadband acoustic absorption structure based on deep ring slits

Abstract

For resonant cavity-type low-frequency broadband acoustic absorbing metamaterials, the broadband acoustic absorption performance relies on the coupling of multiple acoustic absorption peaks. The restriction of small pore size results in a decrease in the bandwidth of individual absorption peaks as the number of coupling units increases and the surface area of the structure expands. Notably, this phenomenon manifests more prominently at lower frequencies. Meanwhile, the realization of broadband sound absorption relies on the precise tuning of small hole parameters. In this study, we propose a modular structure of depth annular slits based on the micro-slit structure. The structure is designed with a series of depth annular micro slits with different inner diameters, which greatly improves the capture efficiency of low-frequency sound waves. Achieving a superior low-frequency broadband acoustic absorption effect with a limited number of units. The finite element model and theoretical model of the structure were constructed, and the sound absorption coefficient was calculated. Furthermore, the intrinsic sound absorption mechanism of the structure is elucidated from the perspectives of absolute sound pressure and sound velocity distribution, relative acoustic impedance, and complex frequency plane. Additionally, the impact of parameter variations on sound absorption curves was investigated. To verify the accuracy of the finite element calculations, experimental samples were fabricated for impedance tube experiments. The results demonstrate that the designed structure effectively realizes low-frequency broadband sound absorption with an average absorption coefficient of 0.89 in the range of 350–710 Hz with five units.