Guards aren't talking in Thief

[Menegrothx]

I finally got around of playing Thief the dark project and I've been enjoying myself but I've noticed that guards haven't said a word thus far. Not when I'm eavesdropping/spying on them in the shadows and not when they spot me and attack me.
I'm at the prision in the mission "Break from Cragscleft prision". I do hear all the other ambient sounds though (drunken noise near a bar, the prisioners moaning and so on). Is it supposed to be like this?
I've heard that a big part of the charm in the Thief games is the fact that you can spy on other people's conversations (and maybe catch some clues on where to go/what to do by doing so), and those moments when guards might be onto you but haven't found you yet and talk about it while you're hiding in the shadows. I wouldn't want to miss out on anything, even though the game is fine as it is. So is it normal that the guards are mute (except when you hit them with your sword) during missions 1&2?

[Xeogred]

Yeah something might not be right, pretty sure the guards should always have dialogue. The games are a pain to get running correctly, maybe check GoG's forums for tips or something.