Li Xinwei, Yu Xiang, Chua Jun Wei, Zhai Wei
Department of Mechanical Engineering, National University of Singapore, Singapore, 117575, Singapore.
Department of Mechanical Engineering, The Hong Kong Polytechnic University, 999077, Hong Kong, China.
Mater Horiz. 2023 Jul 31;10(8):2892-2903. doi: 10.1039/d3mh00428g.
Helmholtz resonance, based on resonance through a pore-and-cavity structure, constitutes the primary sound absorption mechanism in majority of sound-absorbing metamaterials. Typically, enhancing sound absorption in such absorbers necessitates substantial geometrical redesign or the addition of dissipative materials, which is non-ideal considering the volume and mass constraints. Herein, we introduce a new approach - that is to simply reshape the cavity, without alterations to its overall mass and volume - to drastically enhance sound absorption. This is achieved by bringing the cavity walls close to the pores where additional thermoviscous dissipation along these boundaries can occur. Experimentally validated, with three sides of the cuboid cavity close to the pore and at a particular pore-cavity geometry, a 44% gain in maximum absorption is achieved compared to the original structure. Through numerical simulations, we fully elucidate structure-property relationships and their mechanisms, and propose analytical models for design and optimization. Ultimately, utilizing this concept, we demonstrate a heterogeneously porous broadband (1500 to 6000 Hz) absorber that exhibits an excellent average absorption coefficient of 0.74 at a very low thickness of 18 mm. Overall, we introduce a new and universal concept that could revolutionize the design principles of Helmholtz resonators, and demonstrate its potential for designing advanced sound-absorbing metamaterials.
基于孔腔结构共振的亥姆霍兹共振，是大多数吸声超材料的主要吸声机制。通常情况下，要增强此类吸声器的吸声效果，需要对其几何结构进行大幅重新设计或添加耗散材料，但考虑到体积和质量限制，这并不理想。在此，我们引入一种新方法——即简单地重塑腔体形状，而不改变其整体质量和体积——来大幅增强吸声效果。这是通过将腔体壁靠近孔隙来实现的，这样沿这些边界就会发生额外的热粘性耗散。经实验验证，对于长方体腔体的三个面靠近孔隙且处于特定的孔腔几何结构时，与原始结构相比，最大吸声量提高了44%。通过数值模拟，我们全面阐明了结构-性能关系及其机制，并提出了用于设计和优化的解析模型。最终，利用这一概念，我们展示了一种异质多孔宽带（1500至6000赫兹）吸声器，在仅18毫米的极低厚度下，其平均吸声系数高达0.74。总体而言，我们引入了一个全新的通用概念，它可能会彻底改变亥姆霍兹共振器的设计原理，并展示了其在设计先进吸声超材料方面的潜力。
