I take care of my 9 month old nephew during the week while my sister is at work. And the boy SCREAMS like no other. He's not upset - but I guess out of either frustration or even elation, he has a very annoying, ear piercing, shrill & high-pitched scream and he does it constantly. Long screams, short bursts of screams, etc. I'm guessing that could also be his way of "communication?"
I'm sure there's no way to get him to stop - I've tried to hush him, but it seems to only make him scream more. My sister says he does it at home too, in public, etc. Does anyone else have a baby that screams? It's gotten to the point where he wakes the other child I watch as well as my own infant. :o(