50kHz pitch shifter - Sonoluminescence

[Toby Paddock]

(Not really a pitch shifter and not even 50kHz, 
but that's what the old subject line said)

Howdy,
A couple months ago I asked for advice on listening 
to ultrasonic signals from my friend's physics experiment:

Sonoluminescence - Attach piezo drivers to the outside 
of a spherical flask, add water, drive the transducers at 
25-50kHz to generate standing waves, introduce a 
tiny air bubble, tune, tweak, and fiddle with it and 
the bubble glows. I've seen it. Bluish-white glow. Another 
transducer acts as a monitor "microphone".

Thanks to all for the help. I built an AD633 ringmod to 
try to listen to the cavitation "ringing" that was visible 
on the monitor waveform. The drive to the flask was 
at about 50kHz. 
Ringmod input 1 was from the monitor transducer 
and input 2 was the carrier from a sig gen. 
Sweeping the carrier of the ringmod up in frequency, 
harmonics could be heard as tones (as you would expect). 

But at about 360kHz was a band of noise with kind of 
a "squishy" quality to it. As bubbles came and went, 
the squishiness varied. It worked! 
Only had one short opportunity to try it, but it did work.

His page (no audio):
http://students.washington.edu/zell4/SL/sonoluminescence.html

Thanks again,
 - -- -  Toby Paddock