Ultra-wide range control of topological acoustic waveguidesa)

Topological acoustic waveguides have a potential for applications in the precise transmission of sound. Currently, there is more attention to multi-band in this field. However, achieving tunability of the operating band is also of great significance. Different from previous studies, this paper proposes to replace the two-dimensional (2D) resonant cavity in the scatterer with an extended three-dimensional (3D) resonant cavity. In this way, a composite acoustic structure consisting of a 2D scatterer and a 3D resonant cavity is constructed. By controlling the position of the bottom of the resonant cavity, the length of the resonant cavities can be freely controlled. In this way, it is possible to achieve continuous control of the operating frequency band by a very simple mechanical method without changing the initial structure. The control range can reach nearly 6 kHz. This paper also proposes a parallel resonance mechanism that can increase the width of the bandgap by 50%. Simulation results show that this method does not affect the topological phase transition of the structure. In the transmission channel formed by two different topological phase interfaces of this topological acoustic waveguide, the acoustic wave has a high-precision unidirectional transmission characteristic that is immune to backscattering. This study provides a reliable solution for an ultra-wide range of controllable acoustic topological components.