I always hear the words and if the text is descriptive enough then I see flashes of imagery.

The strangest experience I had with my inner voice was the process of learning Spanish. Naturally at first, it was stop and think and translate everything. Then it reached a point where my inner voice provided a fast English translation as I read. (Presuming I was familiar with the words / usage.) I remember thinking just how weird that was. Seeing Spanish words, but they came out in English in my inner voice.

Now I read Spanish and only hear in Spanish unless it's something I have to stop and figure out. That's always in English then gets translated to Spanish.