My boyfriend yells at the tv and he gets...?

He gets mad at me when ever I ask him to stop yelling so loud. It's like he's in his own little bubble and doesnt pay attention to anything else when he's watching his sports. When he yells sometimes it startles our 1 year old and she will run to me crying and I tell him don't yell so loud and he tells me to shut up with an attitude just because I asked him not to yell so loud. I think he has an anger problem and when he's watching sports he yells at the players so loud and curses.. he has changed a lot we have been together for 4 years now and in the beginning he was sweeter and he didn't really swear at me.. He is a nice person but his anger is out of control I don't know what to do about it.