Craig Lee wrote:

> I was looking more for simulated sounds, and examples of how to
> generate white noise, pink noise, buzzing, chirping, sirens, etc with
> a small cheapo pic.  Precision isn't necessary, and direct drive with
> a square wave is fine.

  White noise is the easiest insofar as feeding the bitstream from the
PRBSG clocked at a frequency *much* beyond audio is *already* PWM.  I
have no suggestions on pink noise, and the others require little effort
as far as "PWM" goes.

> I am looking for noises that are annoying to animals, but are audible
> and tolerable to humans... perhaps a difficult task.

  Oooh yes!  I'm sure animals would by and large, ignore large amounts
of white or pink noise entirely, and I cannot think of *any* possible
sound that would annoy an animal that I wouldn't *hate*, inclusive of
mating calls etc...

Sven Milton (MILTON MEDICINTEKNIK KB) wrote:

> A quite simple way of generating a quite near white noice (well -
> pink) is to feed a zener diode with a high value resistor.  The zener
> voltage should be around ¸ Vcc, and R about 1 Meg.

  A popular component to use is the reverse-biassed E-B junction of a
common signal transistor which typically breaks down at 5V (use a 12V
supply).  Note that the reverse-biassed E-C junction has a negative-
resistance breakdown characteristic due to the transistor action.
-- 
  Cheers,
        Paul B.