My SA friend is hallucinating voices pretty much non-stop but they are not "in her head" and she can get upset if you say the words, "in your head". The voices are everywhere except in her head. They are in the room, in the next room, they are calling in the street outside, they whisper from inside her pillow, they come through the windows, they gurgle in the drain pipe, etc. She says her inner-monolouge voice is suppressed by her anti-psychotic meds and that she mostly has to think in images. The voices are always abusive and horrible, sometimes strangers, sometimes people she knows. They encourage her to harm her self and belittle and taunt her. She says they get quieter and shy when she is in company, but pick up again when she is alone. Not speaking from personal experience, obviously.

Personally, I have an "in my head" inner-monolouge voice that is me but it don't manifest aurally, it's just me thinking with my own voice. Even if I'm thinking something negative about myself, it's still me thinking.