可听声频段的声学超材料

Audible sound metamaterial

制作了一维周期排列的亥姆霍兹共振器超材料,在空气环境下测试了其在可听声频段声学透射行为.实验结果表明,在2.1—3.5 kHz附近该材料具有透射衰减的吸收峰,利用声传输线理论(ATLM)计算的透射率和实验结果一致,同时由计算的等效阻抗分析可知,实验中出现的吸收峰是由HRs共振的回波反射引起的.另外,实验测试的样品中透射信号分布进一步验证了材料的共振效应,也就是会出现与外加激励反相响应.基于前述的共振模型计算出该材料的等效弹性模量为负.

We fabricated a kind of 1D metamaterial which consists of periodic array of Helmholtz resonators and tested its acoustic transmission at audible sound frequency in air. The experimental results show that a transmission dip appears at the frequency range of 2.1-3.5 kHz. The transmission ratio simulated by acoustic transmission line method （ATLM） is in accordance with the experimental results. From the effective impedance calculated by ATLM, the transmission dip is ascribed to the backward wave reflection of HRs＇resonanee. Furthermore, the transmission pressure distribution measurement of the inner sample clearly demonstrates the resonance effect in the metamaterial, in which there is an out-of-phase response to the driving field. The value of effective modulus is calculated to be negative based on the resonant model mentioned before.