Character voices! Since Austin's an OC, I've decided that my closest headcanon for his voice is that of Andrew McMahon (who's incidentally one of my favorite musicians).
Andrew McMahon of Jack's Mannequin - 20 Question Int...
Both he and Austin are from southern California
Though in MOM Austin was taken from home as a young teen so his Cali accent isn't quite as strong as Andrew's
But some elements of it remain, and they both have the same kind of clipped mid-range-pitch type thing going on.
Austin can't sing for shit, though. 
...and now I just remembered this song. God. This man has so many good songs.
Last Straw-Jack's Mannequin