We report a lightweight tunable acoustic metamaterial with deep subwavelength thickness (e.g., $\lambda /300$) and strong load-bearing capability for underwater low-frequency and ultra-broadband acoustic perfect absorption. The metamaterial is constructed by introducing a rubber coating and an embedded metallic neck into a metallic hexagonal honeycomb Helmholtz resonator. Physically, the quasi-Helmholtz resonance triggered by the rubber coating together with the anti-phase cancellation caused by the embedded neck leads to superior sound absorption. Theoretical predictions of the metamaterial performance agree well with finite element simulation results. With fixed external morphology (e.g., honeycomb-cored sandwich panel) and fixed overall thickness (e.g., 50 mm), key internal geometrical parameters of the proposed metamaterial can be tailored to achieve tunable perfect absorption from, e.g., 100 Hz to 300 Hz. Further, combining such tunable quasi-Helmholtz resonance leads to ultra-broadband quasi-perfect absorption from, e.g., 306 Hz to 921 Hz. This work contributes to designing underwater acoustic metamaterials and controlling underwater acoustic waves.

中文翻译：

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通过准亥姆霍兹共振可调谐的水下声学超材料：从低频到超宽带

我们报告了具有较深亚波长厚度（例如， $\lambda /300$）和强大的承重能力，可实现水下低频和超宽带声学的完美吸收。通过将橡胶涂层和嵌入的金属颈部引入金属六角形蜂窝状亥姆霍兹谐振器中，可以构造超材料。从物理上讲，由橡胶涂层触发的准亥姆霍兹共振以及由嵌入的颈部引起的反相​​抵消导致出色的吸声效果。超材料性能的理论预测与有限元模拟结果非常吻合。利用固定的外部形态（例如，蜂窝芯夹心板）和固定的总厚度（例如，50 mm），可以调整所提议的超材料的关键内部几何参数，以实现从100 Hz至300 Hz的可调完美吸收。进一步，结合这种可调谐的准亥姆霍兹共振会导致从306 Hz到921 Hz的超宽带准完美吸收。这项工作有助于设计水下声超材料和控制水下声波。