Numerical and experimental evidence of topological interface state in a periodic acoustic black hole

Although the topological interfaces in periodic acoustic black holes (ABHs) have been theoretically reported, there is no published experimental evidence to support this. In this paper, we present experimental evidence and the mechanism explanation of such phenomenon. Meanwhile, the topological protection features are confirmed by introducing defects and geometrical imperfections. The structure under consideration is composed of uniform parts and ABHs with symmetry, which is a necessary condition of Dirac cone. Different from previous works, we used a hybrid mechanism (local resonant and Bragg scattering effect) to generate the multiple topological interface states, resulting in multiple topological inversion points (TIPs). The experiment results are in good agreements with the numerical prediction. This work opens new possibility for manipulating the TIPs in a certain range, which was proved to achieve subwavelength wave control and flexible tunability.