[TriLUG] Sound Processing

[Glenn Hennessee]

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


-- 
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