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I was capturing audio using alsa/pulse, or even without any microphone. But always i have this sample static noise.

Similar to those (you can hear the exact noise what i have now):

Sample 1

Sample 2

Sample 3

Sample 4

How do i kill such noise, even without using any microphone?

Follow up: Misterious analogue audio

1) PC1: alsamixer i mute all my mic

2) PC2: i connect my laptop speaker-out to PC1 microphone in

3) PC1: volume 100%

4) PC2: i hear sounds of PC1

That really proves how blindly he is capturing any kind of noises.
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1 Answer 1

up vote 1 down vote accepted

Short answer: you cannot.

Long answer:

  • the noise originates because you have an onboard soundcard that picks up all noise in your computer. This is a test that proves it on almost all pc's I ever tried: plug in your speakers, make sure no audio is playing, and turn the volume to the max. You here noise. Now move your mouse and you should hear a different noise.. So, you cannot do anything about the source of the noise.
  • the noise is almost white noise, which means it contains pretty much all audible frequencies. Hence you cannot apply a digital filter one it, because a filter that removes all frequencies would leave you with silence only. So, you cannot get rid of the noise using audio processing.

The only way to get decent sound in and out of a computer is using an external soundcard (these can be cheap). Or a very pricy internal one.

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So, It appears that i have, successfully obtained a white noise generator? (one way road, either break this motherboard). Or Buy external sound card or Buy a motherboard with Digital microphone in support? –  YumYumYum Nov 28 '11 at 12:27
    
Please see my update, i tested what you mentioned. –  YumYumYum Nov 28 '11 at 12:34
1  
yes, external soundcard is better. Digital in as well, I didn't think of that but it does indeed not pickup any noise from the pc. –  stijn Nov 28 '11 at 12:49
    
You mean, "it does not pickup any noise from the pc". So itself he creating this noise's? (without any mic, i have that static noise too). –  YumYumYum Nov 28 '11 at 12:55
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the noise you see is analog noise, generated by the pc, and picked up by the A/D ('Analog to Digital') converter of the soundcard. The noise is alwyas there, no matter if you use mic in or line in signals. A digital input however already provides a digital signal, so there is no AD converter needed and hence no analog noise that can be picked up. –  stijn Nov 28 '11 at 13:05
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