Broadband low-frequency sound absorption via Helmholtz resonators featuring embedded rings with porous material lining

Abstract

Abstract This paper proposes an acoustic metasurface design based on Helmholtz resonators featuring embedded rings with porous material lining (HRERPL) for broadband low-frequency sound absorption. A theoretical model employing double porosity theory and abrupt cross section theory is developed to investigate the HRERPL’s absorption performance, which is successfully validated by both simulations and experiments. Simulations are conducted to analyze the sound absorption mechanism. The results show that both the embedded rings and the porous material lining are conducive to impedance matching. Parameter analysis demonstrates that broadband frequency tuning of quasi-perfect sound absorption peaks ( α ≥ 0.9 ) is achievable by adjusting the acoustic properties of porous material and the structural parameters of the HRERPL. By controlling the inner diameter and length of the neck, optimize the HRERPL and compare it with the Helmholtz resonators with porous material lining, further demonstrating the exceptional tunability of the HRERPL.​ Forming multiple HRERPL subunits into parallel structures enhances sound absorption performance, and optimized design can further broaden the quasi-perfect absorption bandwidth.​ It is noted that the selection of the optimized frequency bands significantly impacts the outcome. Finally, a parallel structure composed of six HRERPL subunits is designed to achieve quasi-perfect sound absorption across the range of 310 Hz–540 Hz. This result is experimentally verified via the impedance tube test, demonstrating the good low-frequency broadband absorption potential of the HRERPL. This work provides valuable guidance for the design of low-frequency and broadband acoustic absorbing metasurfaces.