Man Xianfeng, Xia Baizhan, Luo Zhen, Liu Jian, Li Kun, Nie Yonghong
College of Mechanical and Electrical Engineering, Changsha University, Changsha 410022, China.
State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body, Hunan University, Changsha 410082, China.
J Acoust Soc Am. 2021 Jan;149(1):308. doi: 10.1121/10.0003059.
Acoustic metamaterials are a class of artificially periodic structures with extraordinary elastic properties that cannot be easily found in naturally occurring materials and can be applied to regulate the sound propagation behavior. The fractal configuration can be widely found in the acoustic system, like characterizing the broadband or multi-band sound propagation. This work will engineer three-dimensional (3D) labyrinthine fractal acoustic metamaterials (LFAMs) to regulate the sound propagation on subwavelength scales. The dispersion relations of LFAMs are systematically analyzed by the Bloch theory and the finite element method (FEM). The multi-bands, acoustic modes, and isotropic properties characterize their acoustic wave properties in the low-frequency regime. The effective bulk modulus and mass density of the LFAMs are numerically calculated to explain the low-frequency bandgap behaviors in specific frequencies. The transmissions and pressure field distributions of 3D LFAMs have been used to measure the ability for sound suppression. Furthermore, when considering the thermo-viscous loss on the transmission properties, the high absorptions occur within the multi-band range for low-frequency sound. Hence, this research contributes to potential applications on 3D LFAMs for multi-bands blocking and/or absorption on deep-subwavelength scales.
声学超材料是一类具有非凡弹性特性的人工周期性结构，这些特性在天然材料中不易找到，并且可用于调节声音传播行为。分形结构在声学系统中广泛存在，比如用于表征宽带或多频段声音传播。这项工作将设计三维（3D）迷宫式分形声学超材料（LFAM），以在亚波长尺度上调节声音传播。通过布洛赫理论和有限元方法（FEM）系统地分析了LFAM的色散关系。多频段、声学模式和各向同性特性表征了它们在低频区域的声波特性。通过数值计算LFAM的有效体积模量和质量密度，以解释特定频率下的低频带隙行为。利用3D LFAM的传输和压力场分布来测量其消声能力。此外，考虑到热粘性损耗对传输特性的影响，低频声音在多频段范围内会出现高吸收现象。因此，本研究有助于推动3D LFAM在深亚波长尺度上进行多频段阻隔和/或吸收的潜在应用。
