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To address the challenging task of effective sound absorption in the low and broad frequency band for underwater structures, we propose a novel grating-like anechoic layer by filling rubber blocks and an air backing layer into metallic grating. The metallic gratings are incorporated into the anechoic layer as a skeleton for enhanced viscoelastic dissipation by promoting shear deformation between rubber and metal plates. The introduction of an air backing layer releases the bottom constraint of the rubber, thus intensifying its deformation under acoustic excitation. Based on the homogenization method and the transfer matrix method, a theoretical model is developed to evaluate the sound absorption performance of the proposed anechoic layer, which is validated against finite element simulation results. It is demonstrated that a sound absorption coefficient of the grating-like anechoic layer of 0.8 can be achieved in the frequency range of 1 294–10 000 Hz. Given the importance of sound absorption at varying frequencies, the weighted average method is subsequently used to comprehensively evaluate the performance of the anechoic layer. Then, with structural density taken into consideration, an integrated index is proposed to further evaluate the acoustic properties of the proposed anechoic layer. Finally, the backing conditions and the boundary conditions of finite-size structures are discussed. The results provide helpful theoretical guidance for designing novel acoustic metamaterials with broadband low-frequency underwater sound absorption.

Keywords:

underwater sound absorption, broadband, transfer matrix method, rubber coating

DOI: 10.1002/msd2.12053

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https://onlinelibrary.wiley.com/doi/10.1002/msd2.12053

Cite this article: Yu C, Duan M, He W, Chen X, Xin F, Lu TJ. Grating-like anechoic layer for broadband underwatersound absorption. Int J Mech Syst Dyn. 2022;2(3): 265-277.

该文亮点：

1. 提出了一种通过内置空气层提高金属格栅-橡胶复合结构低频吸声性能的方法；
   

2. 揭示了金属格栅-橡胶复合结构的水下吸声机制；

3. 提供了一种复粘度模型用于水下吸声系数计算的方法；

4. 分析了有限尺寸结构的边界条件以及背衬条件对结构吸声性能的影响。

Highlights:

1. A method to improve the low frequency sound absorption performance of metal grate-rubber composite structure by built-in air layer is proposed.

2. The underwater sound absorption mechanism of grating-like anechoic layer is revealed.

3. A method for calculating underwater sound absorption coefficient using complex viscosity model is provided.

4. The influence of boundary conditions and backing conditions of finite size structure on the sound absorption performance of the grating-like anechoic layer is analyzed.

作 者 简 介

于晨磊  西安交通大学航天航空学院博士研究生。2018年取得西安交通大学学士学位。主要从事水下吸声结构设计研究。近年来研究了金属-橡胶混杂结构水下吸声结构。