Multifunctional and Multi-frequency Acoustic Metasurface Based on Reconfigurable Slitted Round Tubes

In recent years, acoustic metasurfaces have been proved to be suitable materials for controlling sound propagation and have unique engineering applications in acoustic field. However, the traditional acoustic metasurface designs usually focus on a single unit structure, which usually achieve the control of sound waves at a single frequency. In addition, it is a great challenge for metasurfaces to change the unit sequence when achieving different functionalities. In order to solve these problems, an acoustic metasurface composed of rotatable slitted round tubes is designed in this paper, which can realize same functionality or multiple functionalities at multiple tunable frequencies at the same time. The basic principle of this acoustic metasurface is based on a coding unit of multiple rotatable slitted round tubes with different characteristic frequencies. Based on the digital coding theory, we can realize the interconversion of logical units "0" and "1" by mechanically adjusting the rotation angle of the slitted round tube, so as to realize the control of the focus position and the realization of the sound beam splitting. Numerical simulation results show that the proposed coding unit can precisely control the focus positions and realize beam splitting at different frequencies by changing the rotational angle of the slitted round tubes. The proposed acoustic metasurface has the advantages of adjustable focus, precise control, multi-beam control and multi-frequency adjustment. Our work has great potential for applications in multifunctional compact acoustic devices and is likely to be used in devices requiring multi-beam control and other functional devices with special dispersion requirements.