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luis jure <ljc@××××××××××××.uy> [11-12-10 13:28]: |
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> on 2011-12-09 at 13:55 Michael Mol wrote: |
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> |
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> >I couldn't tell you if it's necessarily "good", but Audacity has a |
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> >noise filter. |
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> |
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> that's exactly what i was about to reply. |
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> |
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> and if you want to try a CLI tool, sox provides a similar utility. |
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> |
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> noiseprof [profile-file] |
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> Calculate a profile of the audio for use in noise reduction. |
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> See the description of the noisered effect for details. |
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> |
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> noisered [profile-file [amount]] |
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> Reduce noise in the audio signal by profiling and filtering. This |
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> effect is moderately effective at removing consistent background |
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> noise such as hiss or hum. To use it, first run SoX with the |
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> noise‐ prof effect on a section of audio that ideally would contain |
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> silence but in fact contains noise - such sections are typically |
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> found at the beginning or the end of a recording. noiseprof will |
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> write out a noise profile to profile-file, or to stdout if no |
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> profile-file or if `-' is given. E.g. sox speech.wav -n trim 0 1.5 |
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> noiseprof speech.noise-profile To actually remove the noise, run |
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> SoX again, this time with the noisered effect; noisered will |
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> reduce noise according to a noise profile (which was generated by |
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> noiseprof), from profile-file, or from stdin if no profile-file or |
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> if `-' is given. E.g. sox speech.wav cleaned.wav noisered |
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> speech.noise-profile 0.3 How much noise should be removed is |
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> specified by amount-a number between 0 and 1 with a default of |
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> 0.5. Higher numbers will remove more noise but present a greater |
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> likelihood of removing wanted components of the audio signal. |
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> Before replacing an original recording with a noise-reduced |
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> version, experiment with different amount values to find the |
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> optimal one for your audio; use headphones to check that you are |
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> happy with the results, paying particular attention to quieter |
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> sections of the audio. |
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> |
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> On most systems, the two stages - profiling and reduction |
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> - can be combined using a pipe, e.g. sox noisy.wav -n |
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> trim 0 1 noiseprof | play noisy.wav noisered |
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> |
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> never compared the results, if you do, i for one would be very interested |
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> in your experience. |
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> |
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> IMO, it's much better to remove noise by small amounts in successive |
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> passes (taking a new profile each time, of course), than trying to remove |
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> too much noise in one pass. |
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> |
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> let us know how it went! |
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> |
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> lj |
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> |
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|
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I have some results now. "Measurement" was only done with my two ears |
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in a before/after-way of doing. No spectrum analysis or other high |
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advanced stuff. |
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|
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Device: Recording was done with a Tascam DR2D field recorder (SDcard |
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recordings), which has a nice sound and a fine stereo image ... and a |
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slightly high noise floor. |
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|
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Test: |
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I set the internal mics of the Tascam to mid |
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gain and pushed the level to max. I think (read: "I dont know for |
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sure") that the level is simply a variable resistor in the signal |
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path. The gain is the amplification level...so the noise comes from |
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this source beside others. No AGC was active. |
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|
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I went into the kitchen, put the recorder on the desk and switch it |
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on. I let it record its own noise for a moment or two and then start |
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to boil water (high freqs in the sound) and I produced other sounds |
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which contain high freqs. |
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|
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After a while I stopped recording. |
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|
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As exspected, the recording was filled with some noise, which was not |
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destructive but fairly audible. |
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|
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I loaded the file into audacity, and used the denoising filter. |
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The result has noticeable less noise but it was still audible. |
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|
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Then I used gwc in conjunction with pulseaudio. I leave all the setting |
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alone and only selected for the Window function "Hanning-overlap-add" |
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and for the Noise Suppression Method "Lober & Hoeldrich", both marked |
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with "Best" in the settings menu. |
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|
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I denoised the same input as above. |
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|
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The result? There was no noise at all anymore -- at least for my ears. |
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Both files were checked using earphones and played with the Tascam |
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instead being played through the PC loudspeakers. |
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In the beginning of the file there were some audible artifacts, which |
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may result from too less read data...but this is guessed. |
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|
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Gwc is a little fragile due the longer period it was not maintained |
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anymore. Its alsa interface simply does not work. |
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|
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But it clearly wins when it comes to denoising. It also supports the |
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removal of other audio artifacts. |
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|
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HTH! |
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Best regards, |
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mcc |