Advanced Processing Option:

Noise Removal with Audacity

Ideally, if you have a nice low noise floor (virtually no sound when you’re not speaking) and good dynamic range (large difference between the quiet and loud parts, where the louder parts punch Audacity’s Recording Level into the yellow or orange), you shouldn’t need to use Audacity’s Noise Removal function. Every time you use an Audacity effect, your recording and voice will sound a little bit less natural, so we always want to keep these transformations to a minimum. Noise Removal can be particularly damaging to the audio, because it involves removing part of the sound.

However, there are cases just like with the Compressor and Normalize functions, where Noise Removal does more good than bad. Use Noise Removal if:

In these cases, Noise Removal can help by removing background noise, increasing dynamic range, and further quieting the quiet parts. Here’s how:

  1. Perform Noise Removal BEFORE applying other effects, such as Compressor or Normalize.

  2. There must be about 2 seconds of quiet (no talking) recorded that includes the background noise you want to remove. If the noise is just electronic noise, this is easy because it’s probably always there and doesn’t change much. If it’s something else, like a jackhammer drilling outside your window that only runs sometimes, then you need to make sure to capture about two seconds or more of that noise.

  3. Select the silence.

  4. Click to enlarge

  5. Click on Effect and then Noise Reduction…

  6. Click to enlarge

  7. Check that the numbers match those in the figure below. Click “Get Noise Profile.” This sets the quiet piece you selected as the noise to be removed.

  8. Click to enlarge

  9. Press Ctrl-A to select the entire track.

  10. Select Effect -> Noise Reduction again

  11. This time, click OK to remove the noise profile you selected earlier from the entire track

  12. Typically, if you perform noise removal on one track for an audiobook, you should do so for all tracks so they maintain a consistent sound.

When you have finished processing your MP3 files you can return to review the Getting Audio Ready section, or proceed to the Audio File Processing with Audacity page.