Re: [gentoo-user] [OT]: Denoising software ?

[luis jure <ljc@internet.com.uy>]

on 2011-12-09 at 13:55 Michael Mol wrote:

>I couldn't tell you if it's necessarily "good", but Audacity has a
>noise filter.

that's exactly what i was about to reply.

and if you want to try a CLI tool, sox provides a similar utility.

noiseprof [profile-file]
        Calculate  a  profile  of the audio for use in noise reduction.
        See the description of the noisered effect for details.

noisered [profile-file [amount]]
       Reduce noise in the audio signal by profiling and filtering.  This
       effect is moderately effective at removing consistent background
       noise such as hiss or hum.  To use it, first run SoX with the
       noise‐ prof effect on a section of audio that ideally would contain
       silence but in fact  contains  noise  - such sections are typically
       found at the beginning or the end of a recording.  noiseprof will
       write out a noise profile to profile-file, or to stdout if no
       profile-file or if `-' is given. E.g. sox speech.wav -n trim 0 1.5
       noiseprof speech.noise-profile To actually remove the noise, run
       SoX again, this time  with  the noisered  effect;  noisered  will
       reduce  noise according to a noise profile (which was generated by
       noiseprof), from profile-file, or from stdin if no profile-file or
       if `-' is given. E.g. sox speech.wav cleaned.wav noisered
       speech.noise-profile 0.3 How much noise should be removed is
       specified by amount-a number between 0 and 1 with a  default  of
       0.5.  Higher numbers will remove more noise but present a greater
       likelihood of removing wanted components of the audio signal.
       Before replacing an original recording with a  noise-reduced
       version, experiment with  different  amount values to find the
       optimal one for your audio; use headphones to check that you are
       happy with the results, paying particular attention to quieter
       sections  of  the audio.

       On most systems, the two stages - profiling and reduction
       - can be combined using a pipe, e.g. sox noisy.wav -n
       trim 0 1 noiseprof | play noisy.wav noisered

never compared the results, if you do, i for one would be very interested
in your experience. 

IMO, it's much better to remove noise by small amounts in successive
passes (taking a new profile each time, of course), than trying to remove
too much noise in one pass.

let us know how it went!

lj