To my knowledge you can seperate the audio track from the video track. So far as the sound effects and other sound FX being ripped from the source audio. Umm im not to sure if that can be done with the software we have avilable to us.
Overthinking, Overanalyzing seperates the body from the mind.
To get the audio from a ripped DVD, you can either: demux the VOB file(s) (there are many programs that can do this), or make sure you set the Audio Output option to Demux or WAV when you process the VOBs in DGIndex.
As for isolating voices, if you are lucky, the audio is 5.1-channel surround and the center channel is most of the primary dialog (and if you are really lucky, without any sound effects or music). If not, then this thread may help.