There's lots of little programs out there for audio ripping. I use one called "DVD Audio Ripper" which has a setting for the audio levels of the rip, and will rip to MP3 or wave. Other programs, like video editors, will demux to elementary streams (to video and PCM) and you can use that.
Note that if you rip an AC3 5:1 stream to 2 channels, the rear channels get combined with the front and the balance can get weird. Best to stay with ripping the 2 channel streams.