Underwater sound absorption performance of acoustic metamaterials with multilayered locally resonant scatterers

Although the conventional locally resonant acoustic metamaterials (LRAMs) have shown better sound absorption performance in the low frequency band, the effective frequency range of the sound absorption performance is quite narrow relatively. To overcome this drawback, a novel type of multilayered locally resonant acoustic metamaterials (M-LRAMs) is proposed in this paper. The sound absorption performance of the proposed LRAMs can be broadened and enhanced by coupled resonance with embedding multilayered locally resonant scatterers into the matrix structure. The finite element method (FEM) is employed to investigate the band gap characteristics and the sound absorption performance of the proposed M-LRAMs. The coupled resonance effects of the scatterers on the band gap characteristics and the sound absorption performance of acoustic metamaterials are studied as well. Moreover, the effects of the physical parameters of matrix, the thickness of each layer, the number of locally resonant scatterers and the materials of the scatterers on sound absorption performance are investigated. Results indicate that coupled resonance can broaden band gaps and engender multiple band gaps, and the M-LRAMs have many advantages in underwater sound absorption over the conventional LRAMs due to the enhanced coupled resonance effects.