To Hear Without Being Heard: First Nonreciprocal Acoustic Circulator Created

Jan. 30, 2014 — Scientists have built the first-ever nonreciprocal circulator for sound that is able to break sound wave reciprocity. The device is a 'one-way road for sound' that transmits acoustic waves in one direction but blocks them in the other. With this device, you can listen without being heard. "Using the proposed concept, we were able to create one-way communication for sound traveling through air," said Andrea Alù, who led the project and is an associate professor and David & Doris Lybarger Endowed Faculty Fellow in the Cockrell School's Department of Electrical and Computer Engineering. "Imagine being able to listen without having to worry about being heard in return." An electronic circulator, typically used in communication devices and radars, is a nonreciprocal three-port device in which microwaves or radio signals are transmitted from one port to the next in a sequential way. When one of the ports is not used, the circulator acts as an isolator, allowing signals to flow from one port to the other, but not back. The UT Austin team realized the same functionality is true for sound waves traveling in air, which led to the team's building of a first-of-its-kind three-port acoustic circulator.