Research on the low-frequency sound absorption characteristics of coiled Helmholtz cavity acoustic metamaterials

A coiled Helmholtz cavity acoustic metamaterial structure, which consists of three perforated plates, two channel layers and an air back cavity, is designed to address the problem of poor absorption of low-frequency band noise by conventional acoustic materials, and the results demonstrate that the absorption peak frequency of this structure is lower than that of a conventional Helmholtz cavity. The finite element method based on COMSOL multiphysics field coupling software is used to analyze the sound absorption characteristics of the metamaterial single-cell structure and to investigate the effect of structural parameter variations on its sound absorption performance. The problem of broadband sound absorption is solved by synergistically coupling two single-cell structures and then by designing the geometrical parameters of the coiled Helmholtz cavity structure, multiple basic units with absorption peaks at different frequencies are connected in parallel to design a multiunit coupled structure with low-frequency broadband sound absorption performance. In addition, the multiunit coupled structure is embedded in a porous material to design a composite space folding metamaterial structure, which can simultaneously absorb both low- and high-frequency noise and achieve a large broadband sound absorption performance above 200 Hz.