Low-frequency sound-absorbing metamaterial based on a series-parallel arrangement structure

Low-frequency noise has a long wavelength, decays very slowly, and is extremely penetrating. Traditional marine acoustic insulation materials have difficulty achieving effective control of this low-frequency noise. In this paper, a series-parallel arrangement structure of a low-frequency metamaterial is designed, which mainly comprises convoluted channels and Helmholtz cavities in series and a sandwich arrangement of multiple cells (as opposed to the traditional parallel arrangement). We use a numerical method to establish an acoustic-solid coupling model for the metamaterial, consider the influence of thermal and viscous losses on its sound absorption performance, and investigate the sound absorption characteristics and mechanisms of the single-cell and multicell structures. The metamaterial designed in this paper shows an average absorption coefficient of 0.97 in the range of 130–145 Hz. An experimental model was prepared by 3D printing, and the intended sound absorption effect was experimentally verified.