naturerecordists
[Top] [All Lists]

Re: noise cancelling

Subject: Re: noise cancelling
From: "richpeet" <>
Date: Tue, 12 Feb 2002 18:44:23 -0000
Well last time I made a suggestion I ran you down a dead end.
But you may enjoy trying your pair of me-64's using one on subject 
and one off. Then try inverting one channel and converting to mono 
and see if you get a reduction in background noise.  

I don't know how the filtering works from a programming viewpoint to 
understand why it defeated your purpose on the test you tried.

I am still trying to understand the cancelling effect I was able to 
achieve and doubt if I will. I will try some more simple and 
controlled tests. But it does look very worthwhile so far.


good luck

--- In  Vicki Powys <> wrote:
> on 11/2/02 11:50 AM, richpeet at  wrote:
> 
> > Ok I tried this in cool edit. I took a Mono track, converted it to
> > Stereo, inverted one track, and reconverted it to mono. Sure 
enough
> > there was no signal left.
> 
> Rich and All,
> 
> I've just tried inverting a sound track in Peak, then mixing it 
with the
> original.  Same result as Rich - complete cancellation of the 
signal, very
> dramatic!  So I thought to make use of this effect by selecting 
just the low
> noise out of a recording (using Q10), then inverting that noise, 
then mixing
> it back with the original.  It has no effect at all.  The fact that 
I had
> passed the signal through the filter seemed to upset the process 
somehow.
> If you wanted to use phase cancellation as a noise reduction method 
from the
> files in the computer, how would you do this?  I guess it is easier 
to use
> band pass filtering, but I'd still like to know how to use phase
> cancellation for noise reduction on processed sounds.  Anyone know?
> 
> Vicki Powys
> Australia
> 
> 
> 
> 
> 
> on 11/2/02 11:50 AM, richpeet at  wrote:
> 
> > Ok I tried this in cool edit. I took a Mono track, converted it to
> > Stereo, inverted one track, and reconverted it to mono. Sure 
enough
> > there was no signal left.
> > 
> > Now I run a ME 67 long shotgun over my 32" dish. My original 
thought
> > was to be able to aim my narrow 32" dish and cya when I overrun 
the
> > preamp on a loud recording received by the dish. But I also see 
that
> > I can pivot my shotgun because of the way I mounted it and will be
> > able to point it at single source noise problems, invert and 
cancel.
> > 
> > How far away can I have the diaphrams of the two mics before I 
can no
> > longer use this technique?  Is 24" to far?
> > 
> > --- In  Klas Strandberg <> 
wrote:
> >> Using a mono parabol, you can have an extra omni outside of it 
and
> > connect
> >> it antiphase. By moving it, you can "tune" your filtering to the
> > noise which
> >> is present. The remaining noise is the noise which is reflected 
by
> > the
> >> parabol "only".
> >> 
> >> Klas.
> >> 
> >> 
> >> 
> >> At 14:21 2002-02-10 +0100, you wrote:
> >>>> Date: Fri, 1 Feb 2002 09:39:46 EST
> >>>> From: 
> >>>> Subject: Re: noise filtering 101
> >>>> 
> >>>> Jeff,
> >>>> 
> >>>> You audio sounds pretty good after being filtered. Here is a 
few
> > things I do.
> >>>> When I have recordings with car noise, I first use the FFT
> > filter to do a
> >>>> 85dB rumble cut for anything below 120Hz. That gets rid of wind
> > noise too.
> >>>> When I use noise reduction, I get the profile from the sample,
> > manually
> >>>> select a line just over the green noise signal, and reduce 
noise
> > by 80dB. I
> >>>> noticed your settings are at 40dB. I usually keep the noise
> > reduction level
> >>>> slider on the low side. Overdoing noise reduction ruins the
> > quality of the
> >>>> audio, so you might have to play around a little. Cool Edit Pro
> > has a hiss
> >>>> reduction plug-in that seems to work better than noise
> > reduction. There are
> >>>> other noise reduction programs available, such as Algorithmix
> >>>> (http://www.algorithmix.com), that may work better than  Cool
> > Edit. I gave up
> >>>> trying to get quality audio anywhere near highways, railroads,
> > and airports,
> >>>> but sometimes that is a luxury that can't be often found.
> >>>> 
> >>>> The only thing you can do about faint recording is to either 
get
> > closer to
> >>>> your subject or get a preamp for your mic. For noisy
> > environments, getting
> >>>> close to your subject is critical for quality recordings. Did
> > anyone ever
> >>>> think of putting a mic with a long cable on a remote 
controlled,
> > camouflaged
> >>>> model boat? Sounds like it could work.
> >>>> 
> >>>> Bruce
> >>>> 
> >>> 
> >>> I experience a continuing growing problem with noise.
> >>> Because of growing population there is always some kind of
> >>> unwanted noise somewhere. You can name them all, plains,
> >>> trains, highways, farmers with machines or a loud radio on
> >>> some populair station. Is it the right way in using all
> >>> kinds of systems afterwards? I experience the same problems
> >>> with overdone or degrading the wanted sound too much by
> >>> cutting too much. With computers today all kinds of
> >>> unbelievable filters can be used. But with severe cutting
> >>> you degrade the wanted sound often too much. I'm wondering
> >>> if it might work when you use a hightech filter between the
> >>> mic and the recorder or by using a shotgun with an out of
> >>> phase random mic for noise canceling. I suppose its not an
> >>> easy task because you have too set the equipment to a
> >>> certain level so your ready for recording instantly. Whats
> >>> your opinion about this?
> >>> 
> >>> Joop Nijenhuis
> >>> 
> >>> 
> >>> 
> >>> To unsubscribe from this group, send an email to:
> >>> 
> >>> 
> >>> 
> >>> 
> >>> Your use of Yahoo! Groups is subject to
> > http://docs.yahoo.com/info/terms/
> >>> 
> >>> 
> >>> 
> >> This outgoing e-mail is scanned for viruses with Norton 2002
> >> 
> >> Telinga Microphones, Botarbo,
> >> S-748 96 Tobo, Sweden.
> >> Phone & fax int + 295 310 01
> >> email: 
> >> 
> > 
> > 
> > 
> > To unsubscribe from this group, send an email to:
> > 
> > 
> > 
> > 
> > Your use of Yahoo! Groups is subject to 
http://docs.yahoo.com/info/terms/
> > 
> > 
> >



________________________________________________________________________
________________________________________________________________________

<Prev in Thread] Current Thread [Next in Thread>
Admin

The University of NSW School of Computer and Engineering takes no responsibility for the contents of this archive. It is purely a compilation of material sent by many people to the naturerecordists mailing list. It has not been checked for accuracy nor its content verified in any way. If you wish to get material removed from the archive or have other queries about the archive e-mail Andrew Taylor at this address: andrewt@cse.unsw.EDU.AU