Try this one:
http://www.avs4you.com/AVS-Audio-Converter.aspx

i tried ripping the sound from an AVI movie i have, and it does work, and very fast.
the ripping converts the audio file to the format of your choice.

by the way, i use their converters quite often and find they work very well and fast.

See: http://www.blu-ray.com/community/gallery.php?member=Gelli
or: Axiom Gallery