Real-Time Steering of Curved Sound Beams in a Feedback-based Topological Acoustic Metamaterial

TL;DR

This paper introduces a feedback-controlled topological acoustic metamaterial that enables real-time, reconfigurable, and robust guiding of sound beams along arbitrary curved paths, mimicking quantum topological effects for advanced sound manipulation.

Contribution

It demonstrates a novel feedback-based approach to actively control and reprogram acoustic metamaterials to exhibit topological phenomena and unidirectional sound beam guiding.

Findings

Reconfigurable sound beam trajectories that are robust against imperfections.

Implementation of quantum valley Hall effect in a feedback-controlled acoustic system.

Development of a non-collocated control algorithm for unidirectional sound propagation.

Abstract

We present the concept of a feedback-based topological acoustic metamaterial as a tool for realizing autonomous and active guiding of sound beams along arbitrary curved paths in free two-dimensional space. The metamaterial building blocks are acoustic transducers, embedded in a slab waveguide. The transducers generate a desired dispersion profile in closed-loop by processing real-time pressure field measurements through preprogrammed controllers. In particular, the metamaterial can be programmed to exhibit analogies of quantum topological wave phenomena, which enables unconventional and exceptionally robust sound beam guiding. As an example, we realize the quantum valley Hall effect by creating, using a collocated pressure feedback, an alternating acoustic impedance pattern across the waveguide. The pattern is traversed by artificial trajectories of different shapes, which are reconfigurable in real-time. Due to topological protection, the sound waves between the plates remain localized on the trajectories, and do not back-scatter by the sharp corners or imperfections in the design. The feedback-based design can be used to realize arbitrary physical interactions in the metamaterial, including non-local, nonlinear, time-dependent, or non-reciprocal couplings, paving the way to new unconventional acoustic wave guiding on the same reprogrammable platform. We then present a non-collocated control algorithm, which mimics another quantum effect, rendering the sound beams uni-directional.