Sound absorption performance of Helmholtz array with embedded rough necks and small back cavities based on weak coupling

Abstract Traditional Helmholtz resonators are limited by their narrow bandwidth. Although a single rough neck can enhance acoustic energy loss, its ability to expand bandwidth is limited. By contrast, multi-neck structures can broaden the bandwidth but require stringent parameter matching and have complex configurations. Here, to address the issue of the narrow effective sound absorption bandwidth of traditional Helmholtz resonators, a parallel Helmholtz array structure with embedded rough necks and small back cavities (HARNB) is proposed, which achieves broadband and high-efficiency sound absorption through a weakly coupled inter-unit resonance system. Finite-element simulations are used to analyze the design principles and sound absorption mechanisms of HARNB, explore the influence of neck radius, length, relative roughness, and relative wavenumber on the sound absorption coefficient, and elucidate the physical mechanisms underlying these parameter effects. The acoustic absorption performance of HARNB is evaluated under both strong and weak coupling conditions. The results indicate that when each unit operates as an ideal absorber, the absorption coefficient of HARNB decreases significantly to ~ 0.6 under strong coupling. In the weakly coupled system, the absorption coefficient of a single unit is ~ 0.6, and its absorption performance is poor when it operates independently. However, weak coupling among units significantly improves the overall absorption efficiency, achieving high-efficiency absorption ( α > 0.8) with a 56-Hz bandwidth in the 261–317 Hz range. The structure’s high-efficiency sound absorption is confirmed by replacing rough necks with smooth ones and conducting experimental tests on HARNB. The experimental results show that HARNB exhibits a high-efficiency sound absorption bandwidth of 257–323 Hz. HARNB provides broadband, high-efficiency sound absorption without requiring precise parameter matching, offering a novel approach for developing broadband acoustic absorbers. This has important implications for applications such as architectural noise reduction and industrial sound insulation.