Zhong Jie, Zhao Honggang, Yang Haibin, Wang Yang, Yin Jianfei, Wen Jihong
Vibration and Acoustics Research Group, Laboratory of Science and Technology on Integrated Logistics Support, National University of Defense Technology, Changsha, 410073, China.
Sci Rep. 2019 Feb 4;9(1):1181. doi: 10.1038/s41598-018-37510-w.
Effective absorption of low-frequency waterborne sound with subwavelength absorbers has always been a challenging work. In this paper, we derive two theoretical requirements for broadband perfect absorption of low-frequency waterborne sound by ultrathin acoustic metasurface under a finite-thickness steel plate followed by semi-infinite air. Based on the theoretical requirements, an acoustic metasurface, a rubber layer embedded periodically with cavities, is inversely designed to achieve perfect absorption at 500 Hz. The metasurface is as thin as 1% of the working wavelength and maintains a substantially high absorptance over a relatively broad bandwidth. The perfect absorption peak is attributed to the overall resonance mode of the metasurface/steel plate system. Besides, high absorption can still be achieved even if the loss factor of the given rubber material cannot meet the ideal requirement. Finally, a strategy to utilize the inherent frequency-dependent characteristics of dynamic parameters of rubber material is suggested to achieve an ultra-broadband perfect absorption. When the frequency-dependent characteristics of the given rubber matrix cannot meet the theoretical requirements, a broadband super-absorption can still be realized by properly designing the frequency position of perfect absorption of the cavity-based metasurface.
利用亚波长吸声器有效吸收低频水中声波一直是一项具有挑战性的工作。在本文中，我们推导了在有限厚度钢板后接半无限空气的情况下，超薄声学超表面对低频水中声波进行宽带完美吸收的两个理论要求。基于这些理论要求，我们反向设计了一种声学超表面，即周期性嵌入空腔的橡胶层，以在500Hz实现完美吸收。该超表面薄至工作波长的1%，并在相对较宽的带宽内保持相当高的吸收率。完美吸收峰归因于超表面/钢板系统的整体共振模式。此外，即使给定橡胶材料的损耗因子不能满足理想要求，仍可实现高吸收。最后，提出了一种利用橡胶材料动态参数固有频率依赖性特征来实现超宽带完美吸收的策略。当给定橡胶基体的频率依赖性特征不能满足理论要求时，通过适当设计基于空腔的超表面的完美吸收频率位置，仍可实现宽带超吸收。
