I'm not plugged into the gaming community, but I know that gaming headphones are a big industry, and they might be a partial solution that's worth the investment. There are all kinds of headphones, including some that allow ambient noise into your ears and some that don't, and many with microphones designed to only pick up what you're saying and not what's happening around you. Reddit has a gaming headphones forum where you can request recommendations for your computer, what you're using them for, and your budget. I'm on there today, trying to find my husband a set with good mic monitoring so he can hear how LOUD he is being and not traumatize everyone in the house and probably all of his D&D buddies.
If you can work with a sound machine or music, adding headphones will mean one more level of sound absorption between yourself and the screamy kids.
I'm sorry this is happening! My current batch of kids is in the 18-24 mos range, and they are pretty shrieky. I take them inside when it gets out of hand, but they're definitely louder at this nominally-verbal age just for the fun of it, and they're pushing boundaries and don't have the compassion that develops later. Reasoning and laying down rules works better with older toddlers. At this age, I'm just trying to prevent the undesirable behaviors from becoming habitual. I transition the kids from one activity to another any time somebody starts to lose it or decides to make trouble for their own entertainment, but with this age group, that is pretty much nonstop. When it comes to the sounds that other humans are making, there aren't any ways to make them stop that are legal.
Sometimes I daydream about that
Get Smart Cone of Silence.