基于分形曲线近零密度声学超材料的声波调控研究

Acoustic wave modulation and control in fractal curve-based near-zero density acoustic metamaterials

结合空间卷曲理念和分形自相似原理,提出了一种具有“之”字型特征的空间卷曲型声学超材料,利用等效参数法提取了该分形声学超材料结构单元的等效质量密度,结果表明,在特定的频率范围内该分形结构单元具有近零密度特性。有限元法分析结果表明,利用该近零密度分形结构单元进行特定的周期性排列后组成的声学超材料,可以在特定频率范围内实现高效调控声波的目的,例如实现声隐身、声隧穿、弯曲狭缝传输和波前整形,同时分析了这些声特殊现象的出现与近零密度声学超材料透射系数峰值频率的对应关系。最后进行了试验验证,利用3D打印技术加工制得1阶、2阶近零密度声学超材料单元样品,并测试其透射系数,通过对比可知,实测结果和有限元分析结果符合良好,证明了结果的准确性和所设计结构的有效性。

A novel spatially curved acoustic metamaterial was introduced,incorporating the principles of spatial curvature and fractal self-similarity.Utilizing the equivalent parameter method,the effective mass density of the fractal acoustic metamaterial unit cell was extracted,revealing near-zero density characteristics within a specific frequency range.The finite element analysis demonstrates that arranging these near-zero density fractal unit cells in a specific periodic arrangement forms an acoustic metamaterial capable of efficiently controlling acoustic waves in a targeted frequency range,achieving objectives such as sound invisibility,acoustic tunneling,bending of narrow slit transmission,and wavefront shaping.Concurrently,the correlation between the occurrence of these acoustic phenomena and the peak frequency of the transmission coefficient in the near-zero density acoustic metamaterial was analysed.The experimental validation was conducted through the fabrication of 1st and 2nd order near-zero density acoustic metamaterial unit cell samples using 3D printing technology.The transmission coefficient tests were performed,and a comparison with finite element analysis results demonstrates a good agreement,affirming the accuracy of the results and the effectiveness of the designed structure.