[Interest] Simple code to remove backgruund noise from audio sample

[Atlant Schmidt]

Arun:

  Bo's correct - this topic isn't specific to Qt.

  However, just to get you started, I'll make several observations:

    1. The best place to do audio noise reduction is when you capture your
        original data. Use a more-directional microphone, use a secondary
        microphone that is just capturing the "background noise" and subtract
        that out from the primary microphone's signal, use wind screens
        where necessary, etc.

  2. Once you've captured your audio, of course that opportunity has
      passed. At that point, most modern noise reduction is done in the
      frequency domain rather than the time domain. The audio signal is
      often run through a Fast Fourier Transform and converted into a
      series of frequency bins. These content of these bins are then analyzed
      and modified and the signal reconstructed by running it through an
      Inverse Fourier Transform. In this process:

        a. Constant background tones can be removed by zeroing
            out their bin; that frequency will be missing in the output
            but often won't be noticed by humans as missing.

        b. Hiss can be removed by "thresholding" all bins downward
            by a certain amount or by noticing, during silent periods, which
            bins still contain signal and just thresholding down those bins.

        c. The overall amplitude of the signal can be evaluated and all
            bins can be clamped off when the signal is quiet.

  Operating in the frequency domain, this can all produce better (sort-of
  "self-interpolating") results than when you try to operate in the time domain.

  This isn't meant to be a complete list but just something to start you Googling.

                          Atlant

From: interest-bounces+aschmidt=dekaresearch.com at qt-project.org [mailto:interest-bounces+aschmidt=dekaresearch.com at qt-project.org] On Behalf Of Arun Kumar
Sent: Saturday, May 26, 2012 02:52
To: interest at qt-project.org
Subject: [Interest] Simple code to remove backgruund noise from audio sample


Hello,

I am developing one simple audio processing application in C++ using Qt.It can record audio from microphone. When I play the recorded sound there is lots background noise in it. Is there any simple code I can remove the background noise from audio sample

I tried to replace zero to the below audio sound but the recording coming through choppy and I searched in net for noise reduction methods found some algorithms that all are very difficult to understand and implement in my code


Any code sample will very helpful to me


Many thanks,
Arun kumar


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