Is he calmer in your arms or still crying? I have had some children stop that just needed to cry. When they were crying I had to leave them...as even looking in their direction would set them off. For some reason just leaving them to sit on the peripheral of the room watching (even when crying) seemed to keep them the calmest.

I do have extra snack times during the first week or so...and simple easy foods as I find they often eat little and when they are upset, tired AND hungry everyone suffers all the more.

At 11 months they can be left, with toys nearby, out of the middle of the commotion but where they can watch. Rotate the toys he has in reach every 20min or so if he allows it.

If holding him does calm him then set up a routine of some sort...hold for 5min while doing something then 15min on his own. Have him sit on your lap while you are seated. I make a point of not holding the children on my feet as I find it sets all the kids off (11-15months) they all come stand at my feet wanting up. They seem unsettled when I am up like I am leaving or something. If I am seated they play independently and come in for quick hugs as needed.

Wear foam ear plugs in one ear (the side you hold him in)...it can help muffle the sound but still allow you to hear the others.