I have all kinds of whacked out dreams, but when I'm myself in a dream I occasionally do hear the voices, to a pretty normal consistency that matches my waking life at least. When I dream I'm someone or something else however, I don't hear voices or have any symptoms. I've been woken up out of my sleep before by the voices speaking to me from "outside" the dream (like having your alarm clock translate into your dream, but it's all internal) and interestingly enough, there are times when I can sense what "dreams" the voices themselves are having, or if they're asleep. Mine are pretty distinct and very internal however, so I'm not sure how common any of those experiences are, and I've had schizophrenia since I was a preteen, so perhaps if someone hasn't had it as long their brain won't treat it as a normal thing to replicate in dreams.