薄膜型声学超材料的低频吸收性能研究

Analysis on the low frequency acoustic absorption performance of a metamaterial membrane

设计一种能够有效吸收低频声波的镶嵌薄膜结构,镶嵌薄膜结构是由若干个质量-弹簧振子系统和带有硬质边框的硅橡胶薄膜构成。当进入镶嵌薄膜结构中的弹性波与质量-弹簧构成的谐振系统发生共振时,就可实现对低频声波起到理想的吸收效果。研究了镶嵌薄膜结构的声学机理,建立一种局域共振形式的胞元模型,探讨了负有效质量的材料属性。利用有限元仿真模拟,得到了子结构胞元和镶嵌薄膜结构的振动形态,通过谐振单元的理论形式与结构胞元的振动形态进行比较,得到二者吸收机理相同的结论,进一步证明了薄膜对集中质量的牵引力作用与入射声波激励作用的等效关系。同时,对两种不同刚度的薄膜材料进行仿真分析,比较振动形态对声波吸收形式的差异。分别对两种刚度不同的薄膜的声学超材料进行试验研究,同时,研究了结构胞元与周期结构的声学特性关系。结果表明:质量-弹簧系统对低频声波的吸收有很大影响。

A metamaterial membrane with hard frame was presented,which was installed with many small massspring systems serving as low frequency wave absorbers. The mechanical wave transmitted in the metamaterial membrane was absorbed by the spring-mass absorbers at the resonance frequency of the system,which verifies the effectiveness of the sound wave absorption performance of the membrame. Based on the analysis on the vibration mode in local resonance,the negative effective mass was explained by the metamaterial membrane absorption mechanism. The substructure cell and metamaterial membrane modal vibrations were analyzed by numerical simulations. By the comparison between the theoretical form of resonance unit and the model vibration mode of structure cell,the conclusion that both are of the same absorption mechanism was obtained. So,it was proved the effect of the elastic force of membrane acting on the concentrated mass is equivalent to the incident acoustic excitation. The model analysis of two kinds of membranes with different stiffness was carried out and the difference between the vibration mode and the acoustic absorption form was discussed. The metamaterial of the two kinds of memoranes with different stiffness were tested respectively,and the acoustic characteristic relationship between the structure cell and periodical structure was investigated. The results show：that the mass-spring system has significant influence on the low frequency acoustic absorption.