I have both voiced and unvoiced thoughts in my head, depending on what “level” the “thinking” is at. Like others in this thread, I heard every word of this comment as I typed it, as well as a few other times as I ideated and rephrased it before typing. However, some things, particularly practiced things, just happen without any “speaking”, and I just get a notion of the end result. This sometimes leads to a weird thing where, when I’m concentrating on something, both the voiced and unvoiced “threads” will do the same thing, but the voiced thoughts move at the speed of speech, and so the unvoiced thoughts get there first, and then have to wait for the voiced thoughts to catch up. I then get to wonder why I just thought the same thing twice, and why I waited for the voiced thread to finish at all when I already knew the outcome. It’s also not always just my own voice (though usually), I’ll set up “straw-men” to represent a certain viewpoint or person if something needs that level of consideration, or I want to prepare for a difficult conversation (or reflect on one that went poorly) - I’ve seen memes about similar things, so I think that’s pretty usual.

Similarly, when reading, I hear every word (not always in my own voice, characters and narrators sometimes get their own), but if I really get into the flow then parts will move into the unvoiced stream and I get much clearer images of what’s going on (I’m a 1-2 on the aphantasia scale depending on concentration and familiarity) - that state is hard to get to, though.

No idea if any of that’s normal or not, I’ve never really thought to talk to anyone about it.

Also, I occasionally have a small part of the inner monologue slip out as whispered speech too, like you said, though I don’t tend to cover it up, if people ask I just say “oh, sorry, just thinking out loud a bit”.

Edit: added more detail