Enhanced surrounding sound signal acquisition for arbitrary source location by the acoustic higher-order topological insulator

Topological acoustics is a rapidly developing field due to its fascinating topological properties in artificial metamaterials. However, the topological crystals are generally composed of coupled waveguides or resonant cavities, which often leads to fixed excitation positions and excessive structure size, so making them difficult to fabricate and apply in real life. In this work, we proposed an ingenious method to manipulate the coupling between resonant units, which takes advantage of the opening direction of the split-multiple-cavity resonator that can be easily adjusted. Based on this structure, a higher-order topological corner state was observed in both simulations and experiments. More interestingly, the sound energy for the corner state is enhanced and can be excited from outside with a point source at an arbitrary location. This peculiar topological phenomenon may find many applications in sound signal acquisition, transmission, and processing.