DVD Fab Platinum would be the best for this. Not only is it a 100% guaranteed, fool-proof decrypter, but you can rip just the audio like you want, and it will even put it in the correct format for your mp3 player, whatever that may be. I have used the program myself to do this. It also allows you to copy encrypted discs to blank DVD, and lots of other awesome features. See link:
Remove DVD Copy Protection | DVD backup software