[TriLUG] Sound Processing

[Glenn Hennessee]

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