Observation of frequency band-switchable topological edge modes using a 2 bit coding acoustic topological insulator

Abstract

Here, the frequency band-switchable topologically protected edge state transport is realized in simulation and experiment based on a 2 bit coding acoustic topological insulator that consists of two layers of sonic crystals arrayed by the Helmholtz resonant triangle-lattice scatters with two distinct rotation angles. The acoustic topological phase transition is revealed and the gapless frequency bands are predicted. Experimentally measured transmission spectra and simulated pressure fields show good agreement with the predicted results. The error between the measured and the predicted results is illustrated by introducing a slit into the nested scatters, which is comparable to the manufacturing accuracy of the commercial 3D printer. Our work provides a simple method of coding to achieve the frequency-switchable acoustic topological edge modes, and paves a promising way to design the intelligent, programmable, and flexible acoustic devices.