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When I record I always pick up background noise as I don't have a proper studio enviroment. Its usually a constant noise like the computer fan or a low rumble.

I get rid of this with sound forge's noise reduction plug in and its always the first thing I do before adding any other effects or processes to the audio. Works great, but I wonder if there are any processes I could use BEFORE passing the audio through the noise reducer to make the noise reduction better?

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If the noise reducer needed anything before it, it wouldn't be doing a very good job. –  leftaroundabout Oct 25 '12 at 8:47
    
I am new to sound recording, but I have a small signal processing background. If you could record, simultaneously, another track with your noise (or your noise as clean as possible) there are some great simple efficient algorithms to remove the noise (using adaptive filters, or independent component analysis e.g). I wonder if it's standard for DAWs and plugins to have this or if they usually have better ways. –  Rojo Mar 2 at 19:03
    
Ok, I can't find these tools, so perhaps this will end up as a question. Perhaps there's a good reason why. Just in case, if it's easy for you, when recording also put a mic near each important noise source and keep those recordings for later cleanup :P –  Rojo Mar 2 at 19:43

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Without knowing what you are recording:

If the main problem is rumble sound you could use a high-pass filter - that is if what you are recording isn't using a low frequency range. Try with values such as 60-80 Hz as a start point. In you record vocals/voice you can try starting from 100-200 Hz.

Try then to apply a low-pass filter to remove noise in the upper frequency range, f.ex from 8kHz and lower - again, this depends on what you are recording so please adjust as needed.

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Great! This makes so much sense! The recordings I was talking about would be different and not fixed to a low or high frequency but your answer has actually made the noise reduction so much easier and more accurate. –  Aasim Azam Nov 1 '12 at 8:56

You could use a noise gate.

Basically, a noise gate sets a threshold, below which there is silence, above which, the sound can pass. Of course there are other possible configurations involved that will allow you to keep the gate from being a harsh on/off etc.

If the background noise you're trying to eliminate is relatively quiet, and the signal you're recording is not, it could be the ideal solution.

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