Experimental realization of an active time-modulated acoustic circulator

TL;DR

This paper reports the design and experimental demonstration of an active, time-modulated acoustic circulator that achieves non-reciprocal sound transport using actively controlled loudspeakers, enabling unidirectional sound flow in audible acoustics.

Contribution

It introduces a novel active time-modulated acoustic circulator with experimental validation, advancing non-reciprocal acoustic device development.

Findings

Successfully demonstrated non-reciprocal sound circulation

Achieved unidirectional sound transport in audible range

Validated performance with actively controlled loudspeakers

Abstract

Reciprocity is one of the fundamental characteristics of wave propagation in linear time-invariant media with preserved time-reversal symmetry. Breaking reciprocity opens the way to numerous applications in the fields of phononics and photonics, as it allows the unidirectional transport of information and energy carried by waves. In acoustics, achieving non-reciprocal behavior remains a challenge, for which time-varying media are one of the solutions. Here, we design and experimentally demonstrate a three-port non-reciprocal acoustic scatterer that behaves as a circulator for audible sound, by actively modulating the effective mass of the acoustic membranes over time. We discuss the conception and experimental validation of such an acoustic circulator, implemented with actively controlled loudspeakers, in the realm of audible and airborne acoustics, and demonstrate its good performance in different scenarios.