It's a one-way street for sound waves in this new technology

Imagine that you can hear whispers in the room next door, while the lively party in your own room is inaudible for whispers. Yale researchers have found a way to do just that – to move sound in one direction – as part of a fundamental technology, be it mobile phones or gravitational wave detectors.

In addition, researchers used the same idea to control the flow of heat in one direction. This discovery offers new possibilities for improving electronic devices using acoustic resonators.

The findings, from Yale's Jack Harris lab, are published in the newspaper's online edition on April 4. Nature.

"This is an experiment in which we are establishing a unidirectional route for sound waves," said Harris, professor of physics at Yale and lead investigator of the study. "More precisely, we have two acoustic resonators, the sound stored in the first resonator can infiltrate the second, but not the reverse."

Harris said that his team managed to get the result with a "knob" (a laser tuning actually) that could weaken or strengthen a sound wave, depending on the direction of the sound wave.

Then the researchers took their experience to a different level. The heat being mainly composed of vibrations, they applied the same ideas to the flow of heat from one object to another.

"By using our unidirectional sound tip, we can create a heat flow from point A to point B or from B to A, whatever the coldest or hottest," Harris said. "It's like you slide an ice cube into a glass of hot water and the icicles get colder and colder as the water around them gets hotter and hotter. our laser, the heat is brought to flow as usual, and the ice cubes warm up and gradually melt while the liquid water cools a little.While in our experiments, these are not ice cubes and water that exchange heat, but rather two acoustic resonators. "

Although some of the most basic examples of acoustic resonators are found in musical instruments or even automobile exhaust pipes, they are also found in many electronic components. They are used as sensors, filters and transducers because of their compatibility with a wide range of materials, frequencies and manufacturing processes.

The first author of the study is Yale's former postdoctoral fellow, Haitan Xu. Co-authors of the study are Luyao Jiang, a graduate student of Yale University, and A.A. Clerk of the University of Chicago.