Technically inside voices are called pseudohallucinations, while outside your head are proper auditory hallucinations.

When I'm not doing as badly the voices are more internal, and when I was on aripiprazole/Abilify that was working, they were internal before they faded almost completely. The way I think of voices as my thoughts that my brain is getting confused about and attributing to others. So when they're internal, that's less bad/severe than when I think they're totally outside me.

If you are hearing outside voices and they put you in a brain scanner, the bit that is to do with hearing lights up when you have the voices, showing that your brain thinks that it is really hearing something without the external stimuli.

*Willow*