On this note, does anyone know where to get some with an ultrasonic
resonant freq?  Been wanting to make a cleaner for a while but they're
tough to find..

N STEENKAMP [M.ING E&E] wrote:
>
> Hi,
>
> In addition to what was already said:
> Most piezo devices are made to resonate at a particular frequency.
> Driving it at that frequency will give you a good loud beep.  Other
> frequencies are likely to be a lot softer.
>
> Niki