From: "Phil Allison"
Subject: Re: Acoustic Feedback reduction
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Date: Sun, 12 Jan 2003 23:39:37 +1100
NNTP-Posting-Date: Sun, 12 Jan 2003 23:28:56 EST
Organization: Telstra BigPond Internet Services (http://www.bigpond.com)
"John Woodgate" wrote in message
> I read in sci.electronics.design that Phil Allison
> wrote (in ) about 'Acoustic
> Feedback reduction', on Sun, 12 Jan 2003:
> > Do you have a copy of WW May 1974 ?
> > There is a letter ( Howl
> >Supression) from M. Hartley Jones who described a 5 Hz frequency shifter
> >the July 1973 edition. I repeated the experiment he describes with a
> >unit, shifter and headphones. Fascinating.
> > In the letter he says: "I found the absence of beat in the
> >of musical applications rather mystifying at first, but the answer was
> >to lie in the delay between direct and amplified sound".
> Well, that a sort of answer, but not a very deep one. WHY does the delay
> have that effect? It seems unlikely to me that MH-J's 'destroys
> coherence' is the end of the matter. One for Brian Moore, perhaps.
> I can't do any tests myself because the only delay unit I have is a 2
> ohm resistor in a box, and I doubt that half a mho is enough delay.
> On second thoughts, propagation delay is available to everyone, even me.
** The addition of a small delay has little effect on a CRO trace of
the signal - it still shows beats but ya canna hear 'em any more.
The human ear is an intriguing machine - n'est ce pas ?