基于多极子耦合效应的低频宽带吸声超表面研究

The absorption of low-frequency sound is a challenging problem in acoustic research. Traditional sound absorbing materials exhibit linear response in their dissipation factor, which lead to weak absorption capability for low-frequency sound and require extremely huge dimension sizes. These deficiencies cannot fulfill the application requirements of efficient acoustic field manipulation. Recent studies have shown that the artificial resonant units of the acoustic metamaterials can concentrate the sound energy density and dissipate long-wavelength sound efficiently within small sub-wavelength structure, in which rich physics and promising applications are prospected. Acoustic metasurfaces have become a promising future direction in the field of acoustic artificial materials for sound absorbing. However, due to the structural complexity of the resonant elements, the relationship between the resonant mode coupling of the elements and the macroscopic working band is not clear. In addition, the mechanism of impedance matching to reduce the sound reflection is not clarified. Based on previous work, we will make the theory analysis, numerical simulations and experiments to give systematic and thorough research to address the key scientific problems associated with the broadband low-frequency sound absorption in acoustic metasurfaces based on the coupling of multipolar modes. In this project, the applicant will investigate the working band extension by the coupling hybridization of multipolar resonant modes, and make an improvement on the absorption efficiency by impedance matching under near-critical coupling. On this basis, we will develop new acoustic devices according to the novel manipulation effects.

低频声波的有效吸收与屏蔽一直是声学界的难题。传统吸声材料的耗散系数遵从线性响应理论，存在低频吸收微弱、材料厚度过大等局限，难以满足声场调控需求。近期研究表明，声学超构介质的人工共振单元可将声能有效局域从而实现“小尺度”结构吸收“大波长”声波，具有丰富的物理效应和广阔的应用前景，已成为人工吸声材料的重要发展方向。由于微结构人工单元本身的复杂性，其共振模式耦合与有效工作频带的调控关系尚不清楚，且阻抗匹配降低声反射的机理也未澄清。本项目基于已有的人工材料吸声工作基础，从理论分析、数值模拟和实验验证等不同层次，对基于多极子耦合效应的声学超表面低频宽带吸声的关键基础问题进行系统深入的研究，着重开展单元多极子模式杂化耦合相互作用拓展频宽的探索，以及近临界耦合条件下超表面阻抗匹配调控提升吸声效率的研究，并在此基础上构建新原理声学器件。

以小尺寸结构调控吸收大波长声波是低频噪声控制领域的关键瓶颈问题。经典吸声技术受传统多孔声学材料线性响应理论所限，需非常厚重、密实的结构才能有效控制低频声波，难以满足实际应用需求。因此，亟需通过引入超构介质进行低频声场的亚波长尺度调控，发展大波长声波在小尺寸介质中能量密度有效提升和耗散的新方法，为低频噪声控制提供全新思路，并带来声学基础理论的发展及应用技术的革新。针对现有吸声超构表面存在的窄频带、不通风、对称性、方向依赖等不足，本项目从理论分析、数值模拟和实验验证等不同方面，对吸声超表面开展了系统的探索，阐明了微结构单元局域声场共振耦合机制，建立了复合系统耦合相互作用-泄漏损耗调控-吸声性能优化的构建方法，制备了新型轻薄宽带超构表面吸声器件，为解决低频噪声控制的技术瓶颈提供了新手段。取得的代表性成果包括：（1）提出了单元局域声场模式共振耦合状态的精准量化表征与调制理论，发展了可通风非对称吸声体的概念，实现了亚波长结构控制低频声场，并制备了新型超构表面降噪模块。（2）提出了基于复合超表面的水中环境“固液界面声阻抗完全匹配-流体声波向固体振动无反射转化-振动高效局域吸收”的吸声机制，为新原理声学覆盖层的设计提供了新方案。本项目的研究成果发展了利用声学超构表面实现对声波高效局域和吸收等方面进行超常规人工调控的方法，在多种低频吸声体的设计、制备与相关新原理声学功能器件集成等方向取得了多项具有原创性的成果，不但丰富了声学学科的基础理论，还推动了声学功能器件技术的发展。项目支持下已发表SCI论文42篇，包括Nature 1篇、Nature Commun. 3篇、Adv. Mater. 2篇、 PR系列9篇、PRL 1篇、APL 12篇，NJP 1篇、JASA 3篇等，4篇入选ESI高被引论文,产生了一定的国际学术影响。