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Noise in Audio, reducing whiteish noise in audio files
supbreaux
post Feb 11 2010, 18:06
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(Apologies if this is not the correct forum for this topic but it seems to be the most appropriate to me.)

Hello,

I am having a problem with some noise in some of my audio files. Basically it ranges from a soft hiss on some tracks to just fuzziness on others. It does not happen on all tracks and persists despite the system/stereo/speakers I play them on. I believe this to be an issue with the mastering of the original tracks / condition of the media the recording was made from as most of my music is in FLAC or Apple Lossless and does not have the sound characteristics of digital noise / poor encoding.

Its not so much of a big deal normally, and for the most part has been corrected with proper equalization. But recently I have put together a rather nice stereo system and it has become distracting on some tracks.

So here is my question...

Is there any software / method to do analyze my tracks and apply some sort of filter like that used in noise canceling headphones like the ones made by Bose? I realize that this is 'prolly a no luck question but if anyone has any advice on this I would be interested to know.

This post has been edited by supbreaux: Feb 11 2010, 18:08
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DVDdoug
post Feb 11 2010, 19:18
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Yes, you can probably reduce the noise...

First...Noise canceling headphones are something different. In that case, there are two sound sources... The electrical signal and the acoustic/ambient noise. The headphones have a microphone that picks-up the acoustic noise. The signal is inverted and added-in (mixed) with the electrical signal. The inverted signal gets "mixed" acoustically with the ambient sound "leaking through" the headphones to your ear. Mixing the inverted noise with the original noise results in subtraction/cancelation of the noise.

Most audio editors have a noise reduction filter. Typically, you feed it a sample of noise-only (i.e. the noise between songs). Then the software tries to discriminate between the noise and everything else. With constant low-level noise, like tape hiss or a slight background hum, this can work very well. If you have a situation where the noise is very loud, or something like a dog barking, or a truck driving by during an interview, noise reduction usually ineffectivel.


Audacity is a popular FREE (open source) audio editor, and there is a good explanation of noise reduction on their website.

Noise reduction can introduce artifacts (side effects) and sometimes "the cure can be worse than the disease". It usually takes some trial-and-error to get the best results, and sometimes things are best left as-is. This is true of most audio processing... You can easily make things worse!

There is another "filter" called a Noise Gate. A noise gate simply kills (mutes) the audio when it falls below a preset threshold (i.e. between songs). Again, this is something you have to experiment with. It can be distracting/annoying if you hear the background noise cutting in-and-out or if it mutes some of the actual signal. (I'm not sure if Audacity has a noise gate.)

P.S.
The "fuzziness" might be difficult or impossible to remove. It's the kind of thing that a human can detect as "wrong", but it's more difficult for a computer. There are "smoothing" filters and "decrackling" filters made for vinyl transfers that might help with something like this.

This post has been edited by DVDdoug: Feb 11 2010, 19:25
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Arnold B. Kruege...
post Mar 1 2010, 14:38
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QUOTE (supbreaux @ Feb 11 2010, 12:06) *
Is there any software / method to do analyze my tracks and apply some sort of filter like that used in noise canceling headphones like the ones made by Bose? I realize that this is 'prolly a no luck question but if anyone has any advice on this I would be interested to know.


If a system tends to sound noisy, then there is a good possibility that there is some problem in the hardware domain that is either causing or exegarating some minor problem in your pre-recorded media.

Your first test should be direct comparison of how a given file sounds on two different systems.

If you have a system that is an effective file sorter, and tends to make the differences among files more obvious then it is either more transparent than every other system, or it has some ptential flaw that exagerates minor differences that are always there.

In audio production we distinguish between the kinds of production tools that exagerrate flaws so we can hear them and root them out early on, and systems that we listen to for pleasure that tend to put the whole sonic picture into perspective, and are generally more pleasurable to listen to.
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