NGWave Audio/Sound/MP3 Editor: Noise Reduction Part II

This is a continuation of our Noise Reduction tutorial.

Noise Reduction Continued

Let's start with an analog recording. Find a song that contains a noticable hiss in the background. Anything recorded more than a few years ago -- that was not recorded digitally -- should be sufficient.

I recommend using a pair of good headphones when doing this process. Headphones let you hear detail that you may not otherwise hear, and will let you accurately edit the sound, without sacrificing important subtle detail.

Step by Step

The first step is to load up the file, and bring up NGWave's Noise Reduction dialog. In this dialog, you will want to set the controls as follows:

• Frequency: 0.00 kHz
• Threshold: -48.0 db
• Attenuate: -48.0 db
• Fade Out: Medium

With these settings, even with such a low threshold, many analog recordings will already sound better. Click on Preview, and compare with and without the Bypass box checked, and you will see that much of the low-level background noise is removed.

If there's still some background noise present, you will want to move the Threshold slider up. Don't go so far that the normal audio sounds swishy, but far enough that the majority of the unwanted noise is removed. Obviously a very noisy recording may prove impossible to fix, but for most recordings you can remove the background noise without introducing any artifacts -- and end up with a better sounding recording than you started with.

Next, to avoid removing frequencies unnecessarily, bring up the Frequency slider just until you start to hear the unwanted noise again. Note that if you are trying to remove low frequency noise -- such as a 50 or 60 Hz AC line noise, wind noise, or turn-table rumble -- you will likely need to keep this setting at 0.00 kHz. With tape hiss, however, you will likely want to move this up to around 5 kHz or so, depending on the recording.

Then, move the Attenuate slider upward, until the noise is just out of audible range. This allows you to attenuate only to the extent necessary to make the noise unnoticable. The less you attenuate, the less noticable the effect.

The Fade Out can be adjusted to suite. The Fade Out is the rate at which attenuation is applied once a frequency falls below the threshold. Faster fade outs may result in an artificial sound, while slower fade outs may bring more of the noise back into the signal.

Conclusions

With some experimentation, the Noise Reduction feature can be very useful in removing unwanted noise from a signal. Using a good pair of headphones at a sufficient volume level, you should be able to do this without introducing any unwanted artifacts.

This tutorial will be updated to include more tips and information. If you have any comments on this (or any other) tutorial, please feel free to contact us (see the Contact Page for details).

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