Removing noise from a recording with Audacity

Do you have a problem with background noise in your audio recordings? If so, I may have the answer.

Now it is obviously better to ensure that your recording environment is as quiet as possible but that it not always possible for a number of reasons. For example, I usually record on a laptop in our family room area which means that I always have the noise of the laptop fans and, during winter, of the central heating boiler pump. I’d never realised that either of these made a detectable noise until I started recording with a condenser microphone.

I tried everything I could to minimise this, by moving the mic as far away as possible, draping stuff with blankets and bedding, but it still wasn’t enough.

Time to call in Audacity, a superb free, open-source audio editor available for most platforms (Linux, OSX and Windows). If you don’t have this installed on your system then go straight to and download it now. You will not regret it! If you’re going to want to export to mp3 then grab the installer for the LAME encoder from while you’re at it.

One of the things Audacity can do is to analyse a section of your recording that is supposed to be silent, build what it calls a “noise profile”, and then subtract the noise profile from the whole track.

Let me talk you through the steps:

  • When recording, ensure that you have at least 2-3 seconds of silence;
  • Open the track in Audacity;
  • Select the silent section of the track;

  • From the menu choose “Effects”, and then “Noise Removal…”;
  • Click the “Noise Profile” button;

  • Now select the section of the track (usually all of it) from which you want to remove the noise;

  • From the menu choose “Effects”, and then “Noise Removal…”;
  • Preview the noise removal, adjust the settings and, when you’re happy with it, click “OK”. So far I have always been happy with the results of the default values, but you need to pay particular attention to the transition between noise and silence, especially where the audio has a gradual decay, like a sustaining guitar;

  • Audacity saves into its own AUP format. If you want any other format then you need to export it by choosing “File” and then “Export…”
  • Now you’re left with an audio track with silent silences. Bliss.

Here’s a before and after example using an acoustic guitar.

NoiseRemovalBefore.mp3 by davmac

NoiseRemovalAfter.mp3 by davmac

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