One thing that people forget is Foret an his equations...

Harmonics and sums and subtractions...

A super sonic can be heard if it 'beats' with another supersonic
frequency. The difference frequency might be heard and hammers you.

I don't care for the old concept cell / telephone system we have -
chops the low and high - sends middle frequency - So some of us
that have loss in some frequencies have no access to the harmonics.

Martin

On 1/31/2011 10:58 AM, Don Foreman wrote:
On Sun, 30 Jan 2011 16:34:01 -0600, Ignoramus17662
wrote:



This tweeter can deliver a sound pressure level of 94 dB at 25 KHz for
$1.80:
http://www.parts-express.com/pe/show...number=270-011


An alternative: make a Hartmann whistle that runs off a can of freon.
That might take some experimenting, and the sound pressure levels they
can generate could be dangerous.


Don, I recall reading somewhere that high levels of ultrasound may not
be heard, but they can still damage hearing further.

i

I researched this some years ago. What you say is true if the
ultrasound levels are well over 130 dB, intense enough to kill mice in
a bell jar. No risk with a piezo tweeter, might want to be a bit
careful with a Hartmann whistle.