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From: "Phil Allison"
Subject: Re: Acoustic Feedback reduction
X-Newsreader: Microsoft Outlook Express 5.50.4522.1200
Date: Sat, 11 Jan 2003 14:10:13 +1100
NNTP-Posting-Date: Sat, 11 Jan 2003 13:59:47 EST
Organization: Telstra BigPond Internet Services (http://www.bigpond.com)
"g0mem" wrote in message
> "Nico Coesel" wrote in message
> > "g0mem" wrote:
> > >
> > >"Spehro Pefhany" wrote in message
> > >news:email@example.com...
> > >> Many years ago in good old _Wireless World_ (long before "wireless"
> > >> acquired its present meaning(s)) there was a design published for a
> > >> device used to allow higher volume levels in PA systems before
> > >> feedback occurred (with a given microphone). IIRC, they used
> > >> one or two multipliers in a circuit that shifted the audio pitch by
> > >> around 10Hz.
> > >>
> > >> Has this sort of thing been integrated into a single chip?
> > >
> > >I never come accross that method before but there is no reason why it
> > >shouln't work. Another technique to cure feedback on a PA system is to
> use a
> > >graphic equalizer. The method is to turn the volume up until the
> > >occurs, and turn down the appropriate frequency slider on the graphic
> > >the feedback disappears. And repeat until the desired volume level is
> > >obtained.
> > This is really not the way to do it. You'll only make it worse because
> > it will get more difficult to hear what is said through the PA.
> > There is another way though developed by someone named Larssen. He
> > came up with a system that shifts all frequencies by a few Hertz.
> They use graphic equalizers for curing feedback in concerts see:-
> All the above are based on equalization and not frequency shifting.
> Frequency shifting would be OK for speech but not for music and singing.
** So you have never heard it I see.
> soon as you shift the frequency of music even slightly, it goes either
> or Flat depending on which way you shifted the frequency.
** Usually a positive shift of from 2 to 5 Hz is used- this is virtually
undetectable on speech aand most music too.
> Mike Turner
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