Yet an other example for how simple steps can improve the audio quality considerably. The clip below is taken from this blogpost (which I originally found trough Hacker News). You can find the processed version here, or use the controls below to do a quick A/B comparison of the two. The processing was very simple (1. noise removal and 2. running trough the Levelator) and quick.
Crossfade (Original - New):
PS: If you are interested in the simple script which was use to interact with the two youtube players, you can find it in my code repository.