when the game is paused, the processor is not being used as heavily, so it is not generating as much heat. if it is really too loud, perhaps you could replace the fan with a larger one. i had an old Athlon XP PC that had a 60mm cpu cooling fan that was crazy loud. i took it off and rigged up a way to mount an 80mm case fan onto the heat sink, this made a huge difference. a larger fan can move more air, so therefore it doesn't need to spin as fast. now i can barely hear it at all