New spy entrant! A one-way sound machine is here

What about a device that can help people hear someone talking but they themselves cannot be heard. Here comes one.

A team of researchers at University of Texas (UT) has built the first-ever circulator for sound - a one-way road for sound.

Called an acoustic circulator, the device creates one-way communication and can be a game changer for the spying industry.

The fundamental symmetry with which acoustic waves travel through air between two points in space can be broken by a compact and simple device.

"Using the proposed concept, we were able to create one-way communication for sound traveling through air," said Andrea Alù, associate professor at the Cockrell School of Engineering at University of Texas in Austin.

"Imagine being able to listen without having to worry about being heard in return," quipped Alù.

An electronic circulator, used in communication devices and radars, is a non-reciprocal 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 researchers found the same functionality is true for sound waves travelling in air.

"The circulator can transmit acoustic waves in one direction but block them in the other, in a linear and distortion-free way," explained Romain Fleury, the paper's first author.

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, said research.

It also opens up avenues for very efficient sound isolation and interesting new concepts for active control of sound isolators, added the study published in the journal Science.