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Ultrasonic motion detectors

HearWHAC hearwhac at netins.net
Sat Sep 6 00:43:14 EST 1997

mark ross wrote:

> Anybody have experience, information, reports, etc. on the
> interference
> caused by ultrasonic motions detectors (at 25 kHz) on the operation of
> hearing aids?

Several years ago we had a school teacher who had a very real problem
because of one of these devices that was installed in her classroom to
automatically turn off the lights where no motion was detected (energy
saving device). It jammed the microphone of her hearing aid. (The human
hear may not be able to detect a 25 kHz sound, but some hearing aid
mikes can.) The school system eventually made the manufacturer of the
device alter it. They simply changed the frequency to 50 kHz and it
solved the problem..

Harry Teder, a hearing aid engineer recently retired from Telex, has had
more experience with this problem. He once told me that some of the
security devices in stores will jam hearing aids.

Paul Woodard ;-)

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