Ultrasonic motion detectors

[Mike Alf]

On 5 Sep 1997 14:54:27 -0700, markross at UCONNVM.UCONN.EDU (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? 
>
>Mark Ross

I've found that a pure tone sound of sufficient level in that
frequency range saturate the built-in preamp of hearing aid
microphone.  I was using an audio signal generator set at 24 kHz
driving a motorola piezo tweeter aimed at a Knowles 1842 microphone.

Mike