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 http://audacity.sourceforge.net/download/ 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 http://lame.buanzo.com.ar/ 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.
Before:
NoiseRemovalBefore.mp3 by davmac
After:
NoiseRemovalAfter.mp3 by davmac