Sound and heat are put to flow in a single direction

A flexible membrane (gray square) serves as an acoustic resonator, placed between two mirrors. When the laser light gets stuck between the mirrors, it repeatedly passes through the membrane. The force exerted by laser light is used to control membrane vibrations. [Image: Harris Lab / Yale University]

Reversible acoustic diode

A few days ago, you heard of the creation of a tube-shaped acoustic shield that promises things like ending the drone's buzz.

A team from Yale University in the USA has just presented something with similar effect - but not in tube format and with greater versatility.

It is a resonator coupling structure that is essentially a reversible acoustic diode, a structure that allows sound to only go in one direction - in the direction you want it to go.

"This is an experiment in which we make a one-way route for sound waves." Specifically, we have two acoustic resonators, the sound stored in the first resonator can leak to the second resonator, but not vice versa, "said Professor Jack Harris.

Reversible thermal diode

Since heat also consists basically of vibrations, the team repeated the experiments not with sound, but with heat, and the thing worked.

"Using our unidirectional sound trick, we can make heat flow from point A to point B, or from point B to point A, regardless of which one is colder or hotter. hot water and let the ice cubes get colder as the water around them gets warmer and hotter. So by changing a single setting on our laser, we make the heat flow in the usual way, and the cubes of ice gradually cool and melt while the liquid water cools a bit.While in our experiments are not ice cubes and water that are exchanging heat but two acoustic resonators, "Harris detailed.

Steering wheel for heat and sound

While some of the most basic examples of acoustic resonators are found in musical instruments or even automobile silencers, they are also found in a variety of electronic devices, being used as sensors, filters and transducers because of their compatibility with a wide variety of materials , frequencies and manufacturing processes.

With this, the new device can be interesting not only to isolate acoustically environments, but also to guide the heat inside the electronics, all with the turn of a button - in fact, with the adjustment of a laser.

The team now intends to move from its laboratory configuration to more suitable apparatus for practical applications.

Bibliography:  Nonreciprocal control and cooling of phonon modes in an optomechanical system H. Xu, Luyao Jiang, AA Clerk, JGE Harris  Nature Vol .: 568, pages 65-69  DOI: 10.1038 / s41586-019-1061-2