lots of good suggestions, thanks everyone.

I changed the prgram around to step thru some frequencies and
found a more correct freq.  And this will be ear splitting enough
for my purposes.

I thought the little piezo tranducer would act like a speaker, but I
see now that is not really true.

I have been trying different combinations of frequencies and different
durations
and different rates of repeating the tone.  If you repeat it fast enough, it
sort of
rings. - the dog seems to really hate that  ;-)

the amp isn't really necessary, but it worked fine with a higher voltage

I'm going to try the 180 out of phase technique and the push pull next.  -
but it's
already loud enough

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