Thanks for the reply. As an example, I've got two types. One is a self drive and the other is an external drive but both are piezo buzzers. The part numbers (Digi-key) are 102-1146-ND and 102-1135-ND respectively.

If I understand correctly, I can use a 100nF cap in series with the buzzer and hit the resonant frequency (which appears to be 8, 16 or 20 KHz) and it will be loud? If I read the PBP manual correctly, the highest it will be is 20 Khz, correct?

So, with a 100nF cap, one side of the buzzer connected to ground and with this line of code:

SOUND PORTB.7,[250,10]

This should get my ear drums bleeding? :0)