Frequency band-selected one-way topological edge mode via acoustic metamaterials and metasurface.

Single functionality and fixed operating bands maintain the key drawbacks in existing acoustic topological insulators. Here, we report an acoustic system to realize the frequency band-selected one-way topological edge state transmission. The system is combined with a double-layer sonic crystal and a lossy acoustic metasurface. The topological insulators enable the frequency band-selected effect by separating and nesting the two layers of the sonic crystals. The sound one-way transmission effect is ensured by the metasurface. Consequently, the one-way topological edge state transmission is realized, and the operating band of the system can be shifted between two distinct ranges. Our work may have potential in the areas where multiple frequency bands are required, such as sound isolation, acoustic switch, mechanical imaging, acoustic split, and integrated acoustic communications. [ABSTRACT FROM AUTHOR]