I'm sorry guys, but I refuse to believe that the death machines are the end. Yes, it allows us to go further into the story, but why would we do all that work and have to wait months for the next map pack to see what else happens? If it really was absolutely VITAL to the plot, then it wouldn't require all this work to do, they would practically just tell us about it.

Now as NextGen said, the howling voice is constant with every step of the way. We need to indicate this howl. I have personally found just that.

If you look around hard enough, you'll see three red phones - one near the launcher at the centrifuge, and one in the room with the Speed Cola (the third I forget). Occasionally, these phones will actually ring, but I have not found a pattern to determine when they will. However, if you go over to one and hold X, you will hear that howling noise! It's not much help, but maybe the next step is a timed thing - you have to do it at the right time, when the phone is ringing...