"Steve B" fired this volley in news:togf18-
:

Is there anywhere I can buy a simple tone generator, or kit that
will let me build one of these. Is tone generator what I need to be
searching for, or is there another term?


Steve, usually one doesn't use a separate tone generator, amplifier, and
speaker for such purposes -- one uses a self-resonant ultrasonic
transducer for the purpose.

It has the benefit of simplicity -- just feed power and it sings. It has
the deficit of not being able to be tuned to other frequencies -- it's
locked to the one resonant frequency the manufacturer assigned. (that's
usually in the 40KHz range). You can also buy "bare" transducer
elements, but you'll have to build up a power oscillator around them,
which is more work than it's worth, considering the cost of the self-
resonant varieties.

Such transducers may be had on the surplus market with outputs so small
they'll barely be heard by a dog at arm's range, and powers so large
they'll burn up unless mounted in a massive heat sink (or under water).

The bigger ones are used for ultrasonic cleaners and sonar applications.

LLoyd