All four of mine have a different sound to their voice and all their barks are different. I think my Brody has the funniest one he just lets out this really high pitched bark which almost sounds like a loud scream.
Don't feel bad my husband can't tell who is barking either. Even when it's dark and we are all sleeping on the bed together I can tell by feel who is who. DH always says which one is this one. I guess I should be happy he remembers their names LOL.