Earlier quoted context omitted.
I'm pretty sure the "inner voice" is just a metaphor to describe a concept. I, too, do not hear a voice echoing in my head as if God was speaking inside my skull. I have a train of thought that I could directly translate to spoken words, but is not actually in words. It is more abstract; I shuffle around ideas. Sometimes I will speak aloud to myself when I'm trying to disassociate to find a new viewpoint, but that's…
As someone with a very dominant "inner voice", I have to say that, at least to me, it is exactly as having a voice echoing in my head, constantly. More precisely, I happen to think exclusively in dialogues. I imagine talking to a person, and I hear the conversation I would have with that person in my head, and their counterpoints. It gets tiring. Recently I've taken up drawing; when I draw my head is finally quiet.
I'm pretty much the same way. I'm not sure I'd say I exactly "hear" my "inner voice" but my thinking is definitely dominated by "spoken word" stuff.
Of course, I also talk to myself out loud sometimes, when working on a hard problem. Not sure how "normal" that is, but I can't say I really care a whole lot either.