When I talk with my alters there is never any question in my mind that they are not "me". There is never any question in my mind that they are not them. It "sounds" like a conversation in my head with different voices and characters, but they are always discretely and distinctly themselves and each of them is consistent over time. I come to know them as individuals that are definitely "not me".
When I try to go inside and talk to an alter they may or may not "be there" and they may or may not answer me. But if they do answer I can carry on a conversation with them as easily as could carry on a conversation with someone outside of myself (unless we were talking about a topic that either one of us is still dissociated towards). As much as I try to deny the DID from time to time I can't deny the "realness" of the alters. They are just undeniably not me and undeniably real. Which is a real sticking point for my denial at times.
Maybe instead of trying to analyse what they sound like you could try to see what they feel like? The feeling of who we are as individuals is what makes our host accept us as real, because she can't deny that we are here and we are real.