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Keeping the ultrasonic noise down.

Keeping the ultrasonic noise down

Robots that use ultrasonic sensors to measure distances are beginning to appear in factories. However, many manufacturing processes are noisy, and some may generate sounds, inaudible to human ears, that could mask or interfere with such sensors. To study this noise, acoustics researchers Lee N. Bolen and Henry E. Bass of the University of Mississippi in University used a special microphone to measure ultrasonic noise levels at several General Motors Corp. facilities.

The researchers observed that there was little correlation between the sources of ultrasonic sound and the sources of audible sound. "The places that were extremely noisy for a person often had absolutely no ultrasonic sound,' says Bolen. "On the other hand, there were lots of places that didn't sound noisy but where the aerodynamic noise, mainly from nozzles, went on well past 200 kilohertz.'

The most significant ultrasonic noise source was a laser process used to etch numbers on plastic tags. The stretching and relaxing of metal in a tube-bending operation also generated ultrasonic spikes at frequencies up to 1 megahertz.

"For almost all the other systems that we observed,' says Bolen, "the noise fell off very nicely.' High-velocity fluid and air sprays, for instance, were the most common sources of ultrasonic sound, but this faded away at frequencies beyond 200 kilohertz. Robot sensors operating at higher frequencies would not be greatly affected.
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Author:Peterson, Ivars
Publication:Science News
Date:May 31, 1986
Words:230
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