微穿孔黏性超表面的低频宽带吸声机理

Low-Frequency Broadband Absorption Mechanism of Micro-Perforated Lossy Metasurface

针对传统材料难以有效吸收低频噪声且带宽较窄的问题,提出了一种微穿孔黏性超表面的低频宽带吸声机理,并设计了多元胞超表面结构,其中每个元胞由微穿孔板和折叠背腔组成。首先利用有限元仿真和理论公式计算单个元胞的吸声性能,并与传统亥姆霍兹共振器结构进行对比,发现该结构具有优异的高阶峰值,而且峰值带宽增加约1倍,基于此提出了实现低频和宽带的机理;然后分析了典型结构参数对吸声特性的影响规律,如吸声面积比、小孔直径及背腔深度等;最终通过多单元峰值间严格耦合,设计了由8个元胞组成的宽带吸声超表面。结果表明:吸声超表面厚度仅为6 cm,在频段550~2500 Hz范围内实现连续优异的吸声带宽,平均吸声系数高达90%以上。该结构具有厚度薄、频带宽且强度好等特点,在消声室、工厂和航空等场合具有广泛的应用前景。

Aiming at poor efficiency of the traditional materials in absorption of low-frequency sound and its narrow bandwidth,a low-frequency broadband absorption mechanism of the micro-perforated lossy metasurface is presented,and a multi-cell metasurface is designed,in which each cell is comprised of a micro-perforated panel and a coiled-up cavity.The absorption coefficient of a single cell is firstly calculated by finite element simulation and theoretical formulas.Compared with the traditional Helmholtz-resonator structures,the present metasurface structure can gain multiple excellent higher-order peaks besides the first peak,and each peak bandwidth is nearly doubled.Hence the mechanism is proposed to achieve low-frequency and wide-band absorption.The specific effects of the typical parameters on the absorption performance are then investigated,including absorption area ratio,hole diameter,cavity depth,and so on.By strictly coupling the peaks of the cells,an 8-cell metasurface is finally obtained.The results show that the metasurface can achieve continuous and excellent sound absorption in the range of 550-2500 Hz with a deep-subwavelength thickness of only 6 cm,and the average absorption coefficient reaches above 90%.The proposed structure is characterized by the thin thickness,wide bandwidth and high strength,and it can be widely applied to the noise reduction of anechoic chambers,plants and aircrafts.