基于复合弹性质量块薄膜声学超材料低频隔声性能研究

Low-frequency Sound Insulation Properties of Membrane-type Acoustic Metamaterials with Composite Elastic Mass Blocks

传统薄膜声学超材料(Membrane-type Acoustic Metamaterial,MAM)的研究往往忽略了附加质量块与薄膜之间的弹性连接对其隔声性能的影响。为了考虑这种影响,在传统结构的基础上设计三种基于复合弹性质量块的新型MAM结构形式。采用集总参数法推导弹性层刚度变化对传统结构及三种新型结构的固有频率的影响规律。通过三维有限元模型分析四种结构的隔声性能并验证其负物理特性,明确优化结构形式。针对优化结构形式,通过数值模拟进一步详细讨论弹性层结构参数及其相关参数对声传递损失(Sound Transmission Loss,STL)和特征频率的影响规律。研究表明:弹性层的加入不会改变MAM结构的模态振型,但可以降低结构的前四阶固有频率。在总附加重量和总预应力相同的情况下,随着弹性层弹性模量和半径的减小,或弹性层高度的增加,STL峰值向较低频率移动,但STL峰值变化不大。

Previous studies of conventional Membrane-type acoustic metamaterials(MAMs)usually neglect the influence of the elastic connection between the additive mass block and membrane on the sound attenuation properties.In this study,to account for this effect,three novel structures of MAMs with composite elastic mass block are designed on the basis of the conventional structure.The influence laws of the stiffness variation of the elastic layer on the natural frequencies of the conventional structure and the three MAM structures are deduced by lumped parameter method.With the aid of 3D finite element simulation,the sound insulation performances of the four structures are studied and their negative physical properties are verified to select an optimal structure.Furthermore,the optimal structure is simulated numerically and the influences of dimensions and elastic modulus of the elastic layer on the sound transmission loss(STL)and characteristic frequencies are discussed in detail.The results of the study show that adding the elastic layer does not change the mode shapes of the structures,but can lower down their first four natural frequencies.In the case of the same total additional weight and prestress,the STL peak shifts to a lower frequency side with the decrease of the elastic modulus and the radius of the elastic layer,or with the increase of the height of the elastic layer,but the STL peak value only has a slight change.