[quote=Dioxide]
Hmm...Tell me, give me some advice. My character is mute and has never ever thought about having a voice to think in her head, like we all do. What would you write to talk about Sue? :>
[/quote]

Your question is vague at best. Are you asking how you should write thought of someone who has never had a voice? Or are you asking how that would be perceived. Theoretically a thought does not need a voice associated with it, that is a product of our mind putting what we hear with what we think. It is our way of making sense of the intangible. 

However, I find it unlikely that she would not, at some point, not have imagined some kind of voice. We as humans are social creatures and consciously unconsciously attempt to fit in. A person that is mute would most likely choose a voice that they believe is fitting for their personality or has some significance to them. Even the deaf, who cannot hear, can with practice speak their thoughts even though they've never heard a voice.