Removing unwanted Noises from Audio Samples

Creative use of Cool 2000`s Noise Reduction feature

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The Noise Reduction of Cool edit is normally used to remove noises of a continous nature. Here is what the online help says:

Cool Edit 2000's Noise Reduction feature can dramatically reduce background and general broad band noise with minimal reduction in signal quality. It can also remove tape hiss, microphone background noise, 60 cycle hum, or any noise that is constant throughout the duration of your waveform.

But Cool 2000 has also the power to reduce very effectively noises that are not continous at all from certain signals. Normally the signal is varying while the background noise is constant.
Yet it is often the case that the signal remains constant while the noise varies. 
It is always very annoying to find that somebody was coughing right in the quietest passage of  a classical recital. People leave their seats or unwrap their drops.  This can spoil a whole recording. Cool Edit can now help here. The noise is never totally removed but it is often possible to reduce it to an amount that makes it almost unnoticable.

This example shows the tone of a Harp that I sampled last Summer.This very Sample is now part of the Early Patches Akai release. I had visited the owner of the harp to record the instrument in her own home.
Please listen closely to the sample that is provided here
You will notice very clearly a bird that is singing in the background. We all love the little singers. But this time they almost drove me crazy. I was not able to catch the long decay of the harp without a bird interfering. So I decided to record what was possible and to see later what could be done about it.  

You could of course hear the bird. But its sound is not visible in the Waveform view. 
Cool edit provides a great feature with the spectral view (/View menu) to visualize the frequency components of an audio signal. I switched to the spectral view and now You can even see the patches that the bird left on the sample.  


Now how can we get rid of that little tune?  I have used the noise reduction feature to do the trick. Normally it is intended to remove noise but this time I will utilize it to keep the signal. 
To do that an unpolluted portion of the sample is needed that contains all of the frequencies that are present in the  signal. The part shortly after the attack meets our requirements. I will use it as noiseprint or rather as a "signalprint" this time.

After having selected the signalprint I opened the noise reduction dialog (/Transform menu) and took a profile from the selection. This Noise reduction functionality is available to all users of Cool 2000 (and of Cool 96 that I used at the time) even if You do not have the optional noise reduction plugin that offers even more sophisticated features.

Please note that it is very important to use high settings for Precision Factor and FFT Size. Otherwise there will be a noticable click between the processed and the unprocessed portion of the sample. 

After taking the signal print close the dialog. Donīt use the cancel button. This would erase the signal print.  
Now select the betweeted part of the sample and reopen the noise reduction dialog. 
Choose "keep only noise" and set the amount to 100 %.

Hit the OK button. And thatīs it.  

Here is the result. Part of the patches are still visible -  but only when You know exactly where to look for it.

Now listen to the outcome 

An unprepared listener will not be aware that there has been any disturbance at all.

Đ Andreas Sumerauer 1999 Comments?