I know that when I used to use time out it did not go over well. I have since begun using a warning chart, sort of like the stop light scenerio. That works great. Yelling hurts, auditory issues. One hour might be too long, maybe gradually work up to an hour. Picture cards, maybe he is beginning to freak out because he knows the yelling will be coming next. I know this sounds like corporal punishment, but my old OT thought it was the best idea ever, I make my son do pushups (he has only done 5 so far)! lol The deep pressure is good for him and the hard work! ahahahahah Actually now I just say are you ready to do the 5 push ups you wil owe me and he is like NO! lol . I have to do homework with him sometimes 15 min on 15 min off, so maybe instead of being good for an hour start with 15 or 30 min. even 5 if you have to get the point across. baby steps then lead up to the overstimulating steps gradually , won't be noticed as much.