My bro would do this crap to me too. But I was going to work instead of school. I'd tell him to turn it down and guess what brilliant thing he said. "Go to sleep." And I'd tell him "HOW CAN I GO TO SLEEP WHEN YOU HAVE TO SOUND TURNED UP SO HIGH YOU CAN HEAR THEIR FOOTSTEPS!?!?!" He played CoD till 3 in the morning on weekdays. :/
The only way to settle this is to kick his butt out if you can. That was the only way I could fix my problem. I didn't get a good nights sleep untill he moved out. We tried head sets that allowed him to hear the Xbox through them and he would still yell at people and complain about kill steals. X(.