Low-frequency broadband valley transport for acoustic topology based on extended resonance

Abstract This paper proposes an extended resonant structure to solve the problem that topological acoustic waveguides have a narrow bandwidth at low frequencies. This acoustic structure consists of a two-dimensional structure and a resonant cavity in the three-dimensional direction, and its essence is to extend the resonant cavity in the two-dimensional structure to the three-dimensional direction. The problem that the size of the resonant cavity is limited by the size of the two-dimensional structure can be solved by this special extension. At the same time, the resonant cavity can be maximized in the three-dimensional direction. The topological properties of the original structure are not affected as long as the radius of the resonant cavity is widened without changing the symmetry of the overall composite structure. The rotating scatterer remains a reliable method for realizing topological phase transitions. The effect of the resonant cavity length on the band position is obtained using the finite element method, and it is demonstrated that the topological acoustic waveguide has a wide operating band at low frequencies. Simulation results show that this structure still has a bandgap width of 100 Hz at a low frequency of 350 Hz. The topological acoustic waveguide structure proposed in this paper can provide a new idea for the study of low-frequency broadband acoustic topology, which promotes the control of low-frequency acoustic waves by the topological acoustic waveguide.