He tries. He does try to be quiet. There's the kind of pain he's used to...the pain of going for too long with out sleep, the pain of being hungry, the pain of a bullet when you thought you were safe...

The stinging slap isn't pain as he's known it...but it's deliberate. It's even. It just makes him want to give in....surrender.

When the next blow lands, he gasps, but nothing else.