Not sure if this is the right stack exchange site but here goes..
Couple of people at my workplace seem to whisper or quietly speak the material they read. They do this routinely, and they speak more loudly when they don't understand what they are reading. The latter I've done when trying to figure out how the writer intended a particularly complex sentence to be read, but as far as I'm aware when I read I do so silently
This observation arose from a related debate with my partner about reading in one's head- she claims to hear her own voice speaking the words she see when she reads. She doesn't understand my claim that I don't hear any voice, let alone my own..
What mechanisms is the brain employing when it reads? Why do some people vocalise their words, and others imagine themselves doing so? Are these concepts related?