Reading voice

Ok, another really weird consideration, buckle up!  I don't know about you, but I usually re-read all my writings (even all my emails), and I mentally read using my own voice, of course.  When I read emails from somebody that I know, I usually imagine his or her voice.  And when I'm reading stuff from somebody I don't know?  Well, I default back to my own voice.
My way of reading, I guess, implies that I have to go exactly at the same speed as if I was speaking... That's why for me reading a book takes forever!