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

1 min read

Researchers from Yale have created a way to control the flow of sound in one direction in devices that use acoustic resonators, which are found in everything from mobile phones to gravitational wave detectors.

The discovery offers new possibilities for enhancing electronic devices that use acoustic resonators.

"This is an experiment in which we make a one-way route for sound waves," said Jack Harris a Yale physics professor and the study's principal investigator. "Specifically, we have two acoustic resonators. Sound stored in the first resonator can leak into the second, but not vice versa."

Prof Harris said his team was able to achieve the result with a "tuning knob" -- a laser setting -- that can weaken or strengthen the sound wave, depending on the sound wave's direction.

The researchers took their experiment to a different level focusing on heat, which itself consists mostly of vibrations and applied the same ideas to the flow of heat from one object to another.

"By using our one-way sound trick, we can make heat flow from point A to point B, or from B to A, regardless of which one is colder or hotter," he commented. "This would be like dropping an ice cube into a glass of hot water and having the ice cubes get colder and colder while the water around them gets warmer and warmer. Then, by changing a single setting on our laser, heat is made to flow the usual way, and the ice cubes gradually warm and melt while the liquid water cools a bit. Though in our experiments it's not ice cubes and water that are exchanging 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're also found in a variety of electronics. They are used as sensors, filters, and transducers because of their compatibility with a wide range of materials, frequencies, and fabrication processes.