We present an underwater metastructure with excellent sound absorption effect below 50 Hz. The periodic metastructure unit consists of a conical cavity, rubber matrix, and two metal disks. FEM results show that, in the range of 20–300 Hz, the proposed metastructure demonstrates the excellent sound absorption within 279 Hz bandwidth when the reference absorption coefficient is considered to be 0.5. Displacement vibration diagrams illustrate the addition of two layers of metal disks break the propagation law of acoustic wave in rubber matrix. An anti-phase motion of the rubber matrix emerges due to the presence of the metal disks, then consumes the energy of incident acoustic waves. The geometric parameters of lattice constant [Formula: see text], the thickness [Formula: see text], and the height [Formula: see text] of the upper metal disk are positively correlated with the sound absorption coefficient, while the upper radius [Formula: see text] and the height [Formula: see text] of the conical cavity are negatively correlated with the sound absorption coefficient. The novel design presented in this study could have the potential applications in the realization of an acoustic underwater anechoic layer.

中文翻译：

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20Hz以上低频范围内具有宽带吸声能力的水下超结构

我们提出了一种水下超结构，在 50 Hz 以下具有出色的吸声效果。周期元结构单元由一个锥形腔体、橡胶基体和两个金属盘组成。FEM 结果表明，在 20-300 Hz 范围内，当参考吸收系数被认为是 0.5 时，所提出的超结构在 279 Hz 带宽内表现出优异的吸声效果。位移振动图说明添加两层金属盘打破了声波在橡胶基体中的传播规律。由于金属盘的存在，橡胶基体发生反相运动，然后消耗入射声波的能量。晶格常数[公式：见文]、厚度[公式：见文]、高度[公式：见文]的几何参数 上金属圆盘的]与吸声系数呈正相关，而锥形腔的上部半径[公式：见文]和高度[公式：见文]与吸声系数呈负相关。本研究中提出的新颖设计可能在实现声学水下消声层方面具有潜在应用。