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Once you've recorded your podcast, you probably want to clean up the audio before you start editing it heavily. There's a couple of simple things you can do to improve the audio quality in most editors, including the free Audacity editor.

Noise Removal

The first trick is to try and remove as much background noise as possible from your recording. Noise can creep in from a variety of sources:

• Your computer fans etc can be a significant source of noise. if you have the luxury, try to swap them out for quieter versions or install air filters etc. Ultimately though, removing it entirely can be expensive.
• Your own voice can bounce off the walls and desk clutter behind your mic. If you can, try to minimise desk clutter. There are also mic boxes or mini sound booths available that are basically an arc or open-side crate of noise cancelling foam, if you're interested.
• Noise will creep in from your computer connections, especially if you're using an analogue mic plugged into the soundcard through a 3.5mm jack. A USB mic can reduce this, depending on its quality.
• Using your mouse and/or keyboard can create noises, especially if your mic is close to either. It's important to be aware if either causes a problem
• Other noise sources can be from things going on outside, squeaky chairs and so on.

Once you're aware of noise, it's fairly easy to remove it. A constant noise like computer fans can be cleaned in Audacity using the Noise Removal tool. Just select a part of the audio track where no-one is talking to create a noise sample, then apply it to the rest of the track. It won't remove things like coughing, squeaky chairs and so on, but it helps.

It's also worth mentioning that if your podcast is recorded as one track from Skype that it can be difficult to remove all background noise. Skype tends to mute people when they're not talking, meaning that you can get sections where you get someone speaking and their background noise as well. This can be eliminated using double ended recording where each person records their own voice for the editor to then mix down into a single track, but it makes editing more complicated.

Sound Balancing and EQ

Before you mix in your intro/outro music etc, you might want to do some balancing on your audio track. This basically means amplifying it so that the loudest sections are at a sensible level, while the quietest sections aren't too quiet. The Amplify and Sound Compression tools within Audacity help here in order to help producing a balanced vocal track.

The last part to adjust is equalization or EQ. You want to be able to boost certain parts of the vocal recording in order to produce a more rounded sound, while removing those parts of the audio track that are less desirable. Again, a double-ended track can be helpful here, as you can tweak the EQ of each track individually.

An important part of this process is "de essing". This is removing the sharp sounds that creep in when you say "ess". It can be particularly bad if you have a bad cold, a lisp, or a particularly sensitive microphone. To remove this, reduce the EQ gain between 4KHz and 8KHz. Try not to mute it too much as it can make your voice sound flat and lose that crispness. It's worth playing around with various levels in order to get the right sound for you.

Another thing I use a lot is the Noise Removal feature of Audacity. We make sure to leave a section of no talking at the beginning of the podcast and I use that as a sample for the noise. That usually does a very good job of cleaning it up.

For leveling I use the Levelator by Conversations Network at http://www.conversationsnetwork.org/levelator . It does a great job evening out quiet and loud portions of the audio.