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Sound Laser

November 22, 2005

One listener asks: Can sound be directed into a beam, like a laser? The answer might surprise you.


A spotlight of sound. I’m Bob Hirshon and this is Science Update.

Skye Williams of North Potomac, Maryland, asked us whether sound can be directed into a beam like a laser.

Well, Skye, acoustician Jim West of Johns Hopkins says yes. New devices that project clear, focused sound beams are coming on the market. They work by generating ultrasonic waves, which move in a line instead of spreading out. The ultrasonic waves then beget lower-frequency sound waves that we can hear.

JIM WEST (Johns Hopkins University):
And so the audio frequency sort of rides on this high-frequency sound more or less like radio waves. And if you’re not in the beam you don’t hear what’s going on.

These devices are already being used in museums, advertising, and the military. If you have a science question, call us at 1-800-whyisit. I’m Bob Hirshon, for AAAS, the science society.