Characters and authors have different voices, and it can be hard to distinguish the two.
http://www.nownovel.com/blog/talking-character-voice/

Discussion that reminds me of Prep people with great information. (Because we're always looking for great information.)
http://absolutewrite.com/forums/archive/index.php/t-156459.html

This is an interesting take on describing the actual voices and how they sound:
http://www.darcypattison.com/characters/a-year-of-voice-descriptions/