Maybe the pitch of the screaming is really hurting her ears. After my accident I kind of have an insight on how sounds really hurt your head and ears. Different pitches and volumes can sometimes feel like daggers in your ears.
Have you tried headphones? Either listening to music on an ipod or noise cancelling headphones and a secluded area you can direct her too so she can be away from the chaos.

I used to have a tent set up in the corner of my living room with pillows and blankets in it and it was my son's safe place when he felt overwhelmed. In the beginning I had to direct him to it but then he realized it was his safe place to get away from the chaos. I would have earphones in there so if he needed them he could use them.

I hope this helps.

Get his hearing tested, my 26 year old is hearing impaired and loud pitches still hurt his ears. Nancy from, Ga.

I would say buy a set in her favorite color and work with her on keeping them on for 20 secs, 30 seconds, 1 minute ect. until she is used to them and I would definitely do this when your son isn't screaming. I probably would buy your son a pair of his own, imitation goes a long way. I like the ones over the ears with soft cushions (Five and below) for music ones and the cancelling ones the higher the number the better the sound reduction so above a 33 would be great..

Thx Jenny! Any recos for headphones? My daughter doesn't like having things on her head so trying to figure out what style might have a chance of not being rejected ;)