[Arny Krueger]

"Fred." wrote in message


While I don't claim a great ear, I do know that when I
was younger I used to experience discomfort in stores
which left their ultrasonic motion detectors on during
the day. Since this was obviously impossible, you can
imagine that I didn't talk about it much. However, I did
mention it once to my wife, who is a speech pathologist,
snd has some knowledge of hearing science. She, like you
would, discounted it as a minor insanity. Later our
daughter complained of the same problem. Since I never
talked about it with our daughter, I guess it's
hereditary insanity :-).

No, it shows a lack of knowlege by the people making the judgement. Some
ultrasonic motion detectors generate SPLs that would be hazardous to your
hearing, if they operated in the audible range. SPLs in the 112-120 dB are
not unusual. Sensing sound thay is not that far outside the region of the
ear's maximum sensitivity is usually just a matter of getting it loud
enough. Whether you sense sound by means of transmission of the sound into
your ear canal and activation of the basilar membrane, or by other means,
may be a good question.

This needs to be put into perspective with the ultrasonics generated by
musical instruments. As a rule musical instruments generate their maximum
SPLs in the audible range, generally below 10 KHz. This includes most
traditional western-style percussion and brass instruments. Above their
frequency of peak output, response falls off at approximately 12 dB/octave.
Thus their SPLs in the ultrasonic frequency range are far, far less.