Acoustic manipulation allows you to hear without being heard

A system that allows sound to travel in one direction while blocking it from another was recently developed at The University of Texas at Austin's Cockrell School of Engineering. Experiments from a team of researchers using a "circulator for sound" blocked acoustic waves travelling one way. The breakthrough is tipped to pave the way for advances in noise control, new acoustic equipment for sonars and sound communication systems, and improved compact components for acoustic imaging.

“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.”

Romain Fleury, the paper’s first author and a Ph.D. student in Alù’s group, said the circulator “is basically a one-way road for sound. The circulator can transmit acoustic waves in one direction but block them in the other, in a linear and distortion-free way.”

“More broadly, our paper proves a new physical mechanism to break time-reversal symmetry and subsequently induce nonreciprocal transmission of waves, opening important possibilities beyond applications in acoustics,” Alù said.

“Using the same concept, it may actually be possible to construct simpler, smaller and cheaper electronic circulators and other electronic components for wireless devices, as well as to create one-way communication channels for light.”

This research may eventually allow for an “acoustical version of one-way glass,” said Preston Wilson, acoustics expert and associate professor in the Department of Mechanical Engineering.

“It also opens up avenues for very efficient sound isolation and interesting new concepts for active control of sound isolators.”

Research for the acoustic circulator was supported by the Defense Threat Reduction Agency and the Air Force Office of Scientific Research.