To address the dual requirements of underwater low-frequency noise control, a multi-layer periodic composite underwater sound-absorbing material is designed. Owing to its periodic extensibility, the structure can be easily applied to surfaces of various dimensions. The effects of structural parameters, material parameters, and backing boundary conditions on the underwater sound absorption performance are systematically investigated using the finite element method. It is found that the absorption coefficient can reach unity at the second absorption peak, indicating near-perfect sound absorption in the low-frequency range. Furthermore, two types of four-unit parallel combined structures are designed. The first structure achieves efficient sound absorption with coefficients exceeding 0.5 over a broadband frequency range of 44–867 Hz and a peak absorption coefficient of 0.96. The second structure maintains absorption coefficients above 0.5 across 82–1000 Hz, and attains an average absorption coefficient of 0.8 in the frequency bands of 140–500 Hz and 620–1000 Hz. The proposed composite structure realizes low-frequency broadband underwater sound absorption. By combining the low-frequency absorption characteristics of perforated structures and membrane-type locally resonant materials, it enhances the overall structure’s capability to absorb underwater low-frequency noise.
Tian et al. (Wed,) studied this question.