On Wed, 10 Oct 2007 11:12:20 GMT, Winston
wrote:

Don Foreman wrote:
(..)

Those 'ducers aren't good for this. They're either too pricey, too
wimpy or have very limited bandwidth.

Here's what I used:

http://www.electronicpartsforless.co...id=36&df id=1

If ya use a 555 or 556, it needs a simple power amp comprised of a
coupla transistors working from +/- 15 volts.

Bookmarked. Thanks!

--Winston

I used an NE566 or LM566 voltage-controlled oscillator chip so I could
get some frequency sweep. Sweep freq was 60 Hz. This chip is now
long obsolete but there may be others. Ah, Electronic Goldmine has
some, $5.95 ea. The frequency sweep makes a big contribution to how
irritating the sound is.

I put a switch on mine so it could be switched down to a range audible
to humans. When folks would scoff (because commercial units available
did not work), I invited them to hit that switch and stay in the room
with it for more than 10 seconds. One second was usually plenty for
them.