When I read, I whisper all the words, or speak them in a low voice. Technically, I hear my own voice but somehow it is like someone else's voice, a narrator perhaps. I try to hide this when I have to read, say, a newspaper article when other people are around. I have some control over it if needed but the control is not perfect. I have done this as long as I've been able to read.
If there are mathematical formulas or other math stuff in what I am reading, I speak them verbally, too. I'm totally unable just to skip them.