[TriLUG] Sound Processing

[Jim Ray]

Look for a *high* pass filter, not notch.  Telephony ranges from 800 Hz to
3.4 kHz (although I like to run sidetone up to 11 kHz for more perceived
quality).  You definitely don't want anything at or below 60 Hz.  Drop it at
800 Hz and you should be fine.

Regards,
 
Jim
 
Jim Ray, President
Neuse River Networks
tel: 919-838-1672 cell: 919-606-1772
http://www.Neuse.Net
 
Connecting You to the World since 1997
 

> -----Original Message-----
> From: trilug-bounces at trilug.org [mailto:trilug-bounces at trilug.org] On
Behalf Of Glenn
> Hennessee
> Sent: Tuesday, July 10, 2007 11:45 AM
> To: Triangle Linux Users Group discussion list
> Subject: Re: [TriLUG] Sound Processing
> 
> Glenn Hennessee wrote:
> > burnett at pobox.com wrote:
> >> On Tue, 10 Jul 2007, Brian McCullough wrote:
> >>
> >>> I have an issue that has been causing me a great deal of grief over
the
> >>> past while.
> >>>
> >>> I have some sound files ( telephone recordings ) that have a VERY loud
> >>> 60-Hz hum.  They are, at the moment MP3 files, but were WAVs coming
out
> >>> of the recorder.
> >>>
> >>> I am wondering if anybody has and bright ideas for inserting a
> >>> 180 degree out of phase signal to cancel the hum, or any other ideas
to
> >>> clean up these files.
> >>>
> >>> ( The hum seems to be being inserted inside my machine, although I am
> >>> willing to accept suggestions for correcting future meeting
recordings,
> >>> as well as correcting the old recordings. )
> >> For a commercial and non-Linux solution, I use Sound Soap on OS X to
clean
> >> recordings. It has specific 50 and 60Hzremoval settings, as well as
other
> >> more general options. It's done me a great deal of good.
> >>
> >> http://www.bias-inc.com/products/soundSoap2/
> >>
> >> Market blurb follows:
> >> "Mac OS X, Windows XP, Windows Vista, application, plug-in, you name
it.
> >> This cross-platform, multi-format powerhouse includes Audio Units,
> >> RTAS/AudioSuite, and VST plug-in formats."
> >>
> >> If you're interested, send me an email offlist and I can process a
sample
> >> for you for a test.
> >>
> >> Steve B
> >>
> > A search on google gave this:
> > http://www.nabble.com/Removing-background-noise-t4007834.html
> > which suggests the notch filter in the 1.3.3 version of audacity. It's a
> > beta version and you'll have to compile from source for linux. The
> > audacity site says to expect things not to work/crash with the beta
> > version so don't get rid of the stable version. I haven't tried it so I
> > can't make any comments as to how well or if it works at all.
> > glenn
> >
> >
> There is a notch plugin for the stable version of audacity from
> http://audacity.sourceforge.net/download/nyquistplugins and it's about
> halfway down the page.
> glenn
> 
> --
> Glenn Hennessee
> Department of Chemistry
> NC State University
> Raleigh, NC 27606
> Voice: (919) 515-2947 FAX: (919) 515-8909
> Email: Glenn_Hennessee at ncsu.edu
> 
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