> This condition frequently resulted from a combination of three devices
> being interconnected:
>
> a) Microphone (input device)
> b) Audio Amplifier (booster)
> c) Loudspeaker(s) (output device)
>
> Furthermore, this condition is triggered by "POSITIVE FEEDBACK". This
> means that sound waves radiating from the speaker, made their way
> back to the microphone (through the air) "IN PHASE" and, the strength
> (amplitude), exceeds a "threshold" trigger point.
>
> Since the amplifier's job is to amplify (boost) sounds picked up by the
> microphone, and then send them to the speaker (output device), this made
> a "CLOSED LOOP" process.
<snip>
Hmmm... on the hunch that you're going somewhere with this, my guess is
that next you'll be asking if there is a purely-electrical (or
electro-mechanical) equivalent of this phenomenon, right? Speaking of
which, would such an arrangement qualify as a type-2 perpetual motion
machine (according to Thermodynamics, a perpetual motion of the second
kind would be an action which causes additional energy to be converted
into a useable form, causing 'over-unity' --- can the natural resonating
action displayed here be used to cause a simple form of free energy using
accoustics?) ... oooh, the worms - the can of worms this opens, man! <g>
[note: and not *ONCE* did we mention the three-letter g-word <sorry,
couldn't resist>.] :)