alt.sci.physics.acoustics

On Fri, 19 Oct 2007 23:16:39 -0700, "Green Xenon [Radium]"
wrote:

>On May 28, 10:27 pm, Benj wrote in
>http://groups.google.com/group/sci.energy/msg/17e8728d2165c087 :
>
> > Radium wrote:
>
> > > Could a similar process be done in acoustics? IOW, something like
> > > using four 1 KHz sine-wave tones to produce 4 KHz sine-wave tone? If
> > > so, how would this be done?
>
>
> > Yes, it can but you have to send them through the appropriate non-
> > linear devices!
>
>
>Just what are these "appropriate non-linear devices"?

Well, in analogue electronics, there's a thing called a "ring tone
modulator" or a "four quadrant amplifier" (it also goes by other
names), which produces output frequencies that are the sum and
difference of the frequences that you present to its inputs.

If you're familiar with "Doctor Who", it's the gadget that they use
for the Dalek voices, to produce the harsh modulation effect and the
artificial-sounding metallic overtones
(I built one in a coke can when I was a kid ... a ring tone modulator,
not a Dalek).

A purely acoustic or mechanical version would require more thought.

Eric