How to take audio from a youtube video

[Lord]

Does anybody know how to take the audio from a youtube video and convert it in Mp3 for me to work in audacity?

 

[Monsieur Xavier]

Google knows links

 

[Lord]

Thanks.
But how do i take the audio from this?
http://moodle.es-pr.net/file.php/49/Mod5/bart.wav