The Temperature of Sound
U Professor Uses Noise to Create Refigeration
By: Wynne Parry
Issue date: 3/2/01 Section: Feature
|
Their cries interrupt undergraduate Matt Emmi as he describes the work going on behind him.
Over three years ago, he took a class on the physics of audio and video, and then came to work for the man who taught the course.
“The professor is always doing interesting things,” he said.
He explains that the two students making noise in the corner behind him are experimenting with small devices that turn heat into sound.
Orest Symko—the professor—wearing a tie under a brown wool jacket with elbow patches, arrives to confer with Emmi.
Once back in his office again, Symko sits at his desk. Lazy notes of Brazilian jazz drift from the stereo near the window.
He introduces his work in thermoacoustics with a touch of history. Heat engines have been around since the 1800s, he explains.
To demonstrate he stretches out his palm and places the circular base of a pinwheel-like machine on it.
Several degrees of warmth from his hand drive a piston into action. It spins a clear plastic disk, decorated with two strips of hologrammatic silver.
Just as heat produces motion, it can also generate sound, a phenomena first noticed by glass blowers more than 200 years ago.
Now Symko is using a similar principle to create tiny refrigerators that could be used to cool the circuitry in computers and other electronic devices.
He has carried a handful of the small devices from the downstairs lab and scattered them on the desk in front of him.
Made of a variety of metals, some vaguely resemble cylindrical bits of pipe, closed at one end with white teflon bands around the center.
With his fingertips, Symko dips the end of one of the metal devices into liquid nitrogen. This creates a difference in temperature and drives heat flow along its length. Wisps of vapor lap at his fingers, and after several seconds he lifts the device.
A shrill tea-kettle-like whistle emerges from the open end of the inch-long device. He explains that the flow of heat between the warmer and the cooler ends creates the sound.