Sooner or later, there will be an audio file you need that isn't quite right. You may be able to use Audacity to whip it into shape. There are free versions for most platforms and a bunch of free software plugins for many routine audio editing chores. Audacity may turn out to be all you need for handling audio files.

It came in real handy while working with the Zoom H4 recorder. When running that recorder on batteries, an audible beep often gets introduced into the recordings. Quite annoying. Using Audacity with the Nyquist Notch Filter plugin, it's pretty easy to clean up those artifacts. Cutting out unwanted silence and fading volume in and out is even easier to accomplish.