Strange Technology

Invention: One Way Sound

This is the best strange news item I read today: one way sound technology from Yale university. If this makes it to the consumer market, it will be a most welcome invention for recording engineers and many others.

Imagine being able to hear people whispering in the next room, while the raucous party in your own room is inaudible to the whisperers. Yale researchers have found a way to do just that — make sound flow in one direction …
The findings, from the lab of Yale’s Jack Harris, are published in the April 4 online edition of the journal Nature.
“This is an experiment in which we make a one-way route for sound waves,” said 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.”
Harris said his team was able to achieve the result with a “tuning knob” — a laser setting, actually — that can weaken or strengthen a sound wave, depending on the sound wave’s direction.
Then the researchers took their experiment to a different level. Because heat consists mostly of vibrations, they 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,” Harris said. “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.
Via Yale

… Other electronic advancements are also in store with this new kind of technology. Musical instruments would get some major upgrades, as well as exhaust pipes found in cars.

Via TechTimes

After reading the article above, I can’t say I understand exactly what they have done.
They used lasers applied to a barrier. Lasers are light, so how did they get “optically induced mechanical nonreciprocity” to make sound go through the barrier in only one direction? I skimmed the published article in Nature and understood a bit more, but still didn’t really get it.

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