Shellymos:
Our DS turned 5 a couple of weeks ago. We do see crazy behaviors sometimes - not dissimilar from the kind you describe - but they haven't been as constant. In our case I think the silly noises are a different thing from the impatience and screaming. We also have the music in the background issue - our DS is constantly whistling - but since I do that too I can't really complain.
I deal with the silly noises differently from the screaming. Screaming is something we don't tolerate. If it continues I threaten to take away something valuable to him - like his baseball glove - and that usually calms things down. But the silly noises I don't treat that way. One thing I've tried is just to join in. Make it a funny conversation. In our case it becomes a joint game that evolves rules of its own - rhyming rules or funny semantic association rules, for example. Usually he really enjoys playing it for a while, and once it's run its course he moves on to something else. Not sure this will work for you, but it might be worth a try.
Good luck: I know these things can be very frustrating.
BB
