I scream, you scream, we all scream

Lucy and Harper have a new game. This is how it goes:
-Harper screams, a happy scream, but a loud and obnoxious scream, nonetheless
-Lucy "shushes" her
-They giggle.
Repeat, 1 million and 1 times each and every day. The only variation is that Lucy will also scream.
Another fun game:
-Lucy says "mmmmmm!" very loudly, as in "mmmmm, this food is really good!"
-Harper also says, "mmmmmmmm!" even louder.
Repeat 1 million and 1 times each meal time.
It has gotten old. It has been about a week since this started. What this means is that I have had a week not only of listening to these not-fun games, but I have also had the joy of hearing it first thing in the morning when Harper starts it up, wakes Lucy up, wakes me up and eventually wakes Graham up. The same goes for naptimes. With little sleep occurring on my part, this is not a game I want to continue. Ask Harper, she went to tim-e out four or five times today for screaming. Lucy went twice.
I told them they could scream all they wanted outside. Even that had to end today when I had heard it no less than 20 times in 10 minutes. The neighbors should not be subjected to their "games". It can't be ignored and unfortunately, all it makes me want to do is, well, scream.