You can use MPlayer to rip audio from a DVD into a high quality .wav file.
You will need to add the medibuntu repo in order to install libdvdcss.
sudo apt-get install libdvdcss2 mplayer
Pop in your favorite DVD, then issue this command:
mplayer -vo null -ao pcm -ao pcm:file=audio.wav dvd://01
You may have to adjust the last part dvd://01 to dvd://02, or another track.
This command is basically telling mplayer to play back the DVD with no video, and dump the audio as PCM audio to a wav file.