This falls in the normal range. He is just so involved in other things he wants to do, he blocks every thing out. Remember this will be a GOOD skill when it comes to studying or working..
I suggest you call his name, then wait for him to either answer you or look at you. Then tell him whatever. Then ask him "what did I say?" or "What did I just ask you?"
Another thing is to give him a heads up about what will be happening next. Playing a video game? Let him know he has 10 more minutes, then he needs to stop and get ready to go to the store. It can be hard to stop on a dime, when you are involved in something.
"When dad gets home, you need to stop what you are doing and wash your hands for dinner." Then ask him, what did I just say?
The other thing "I do not like yelling across a house. It teaches kids to yell across the house. I always walked towards our daughters room and called for her. Same with our daughter.. I never answered yelling from all the way across the house. I wanted to be able to hear clearly what was being said.
Of course she knew if she was mortally wounded or extremely ill, that was an emergency.
Outside, I would call for our daughter (using her name) and she was to either walk over or at least look at us letting us know that she heard us.. then she was given a moment to stop what she was doing and come over.