I was just re-reading this thread. I know what you mean--even my deaf cat 'hears' me when I say treat. LOL Actually he can see the other cats reacting when I bring out the treats, and then he sees the bag so he has his ways of knowing....
ok, thanks guys! Oberon is not overly macho, but quite sensible, so he probably thinks purring is for the overactive crazy types
Will check his chest next time he sits on me for vibrations, though, that's a great idea. He's definitely not deaf (not when I say "treat").