Bandgap-controlled acoustic interlayers for low-loss topology transmission

Directional induction of acoustic waves has gained increasing attention in recent years. Conventional acoustic topological insulators have drawbacks such as geometrical complexity and difficult processing, which increase the difficulty of engineering applications. In this paper, we propose a scatterer-free and easy-to-machine sonic crystal structure to realize topological acoustic transmission by embedding a cylindrical cavity on a solid substrate. Compared with conventional acoustic metamaterial plates, this structure can significantly enhance the acoustic transmission capability due to the absence of dissipative effect of resonant cavities. The acoustic interlayer structure was designed in parallel, and it was found that band modulation could be realized by changing the distance between the interlayers. This modulation method is different from the traditional method of changing the scatterer structure, which is simpler and more convenient. In addition, the design of the interlayer with no scatterer on the surface allows the placement of various acoustic sensors in the interlayer to realize specific functions. This study provides new design ideas for lightweight devices, high-precision acoustic sensing and low-loss acoustic devices. It also provides a more convenient and effective tuning method to accelerate the engineering of acoustic metamaterials.