[LAU] denoising audio files

Thomas Vecchione seablaede at gmail.com
Thu May 24 14:20:09 UTC 2012

On Thu, May 24, 2012 at 10:04 AM, Kevin Cosgrove <kevinc at cosgroves.us>wrote:

> On 24 May 2012 at 13:52, Fons Adriaensen <fons at linuxaudio.org> wrote:
> > So that's at least three cases
> >
> > 1. Unwanted ambient noises
> > 2. Tape noise
> > 3. Vynil noise
> Other cases I've faced are:
> 4. Power line hum getting into the recording system.
> 5. Acoustic hum from florescent lights.
> 6. Noise from photocopier drum warming getting into
>   the power circuit with chirps every 12.6 seconds.
> I think Fons is onto something, find the cases for noise
> reduction, study the noise content, and devise or apply a
> suitable noise algorithm.
This is standard practice for anyone that does restoration work.  What Fons
has said, not to demean it at all, is common knowledge for those that use
the tools.  Your standard 4 tools are a broadband de-noiser, used for
relatively constant noises in the background, often a multiband expander at
least when dealing with realtime applications.  A De-Buzzer designed to
take at periodic noises that have relatively high harmonic content at
regular intervals, primarily a series of carefully designed notch filters.
A De-Hum which is designed to take out periodic noise without much harmonic
content.  And a De-Clicker designed to remove clicks and pops you get from
vinyl and other sources (ie. Dust on Tape going over the heads sometimes).
But also as he mentioned you can get more specialized tools as well and yes
some will go so far as to allow you to focus on specific spectral areas, if
anyone has seen Audition this does this, but really I am referring to much
more specialized tools that cost much more money, like Algorithmix

There is an 'ok' article on the basic process located on CEDAR Audio's
website, who are pretty much the standard in the industry to my knowledge
for realtime noise reduction(As compared to Algorithmix reNovate which is

Click on "About Audio Restoration"

At least it covers the basics pretty well if you click through to info on
the various tools at the bottom of the page.

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