I wouldn't say I literally hear the voice; I can easily distinguish it from sounds I'm actually hearing. But the experience is definitely auditory, at least some of the time; I could tell you whether the voice is male or female, what accent they're speaking in (usually my own), how high or low the voice is, and so on.
I definitely also have non-auditory thoughts as well. Sometimes they're visual, sometimes they're spatial, and sometimes they don't seem to have any sensory-like component at all. (For what it's worth, visual and spatial thoughts are essential to the way I think about math.)
If you want to poke at this a bit, one way could be to test what sort of interferences disrupt different activities for you, compared to a friend.
I'm thinking of the bit in "Surely you're joking" where Feynman finds that he can't talk and maintain a mental counter at the same time, while a friend of his can -- because his friend's mental counter is visual.
Another month has passed and here is a new rationality quotes thread. The usual rules are: