Got a smart cover? Just peel it back and let it cover the under side of the Air 2 while holding it. You will basically not even feel the vibration with the volume cranked.
Oh wait. Now I'll read this adds additional weight to the Air 2.
Padding the back may work but you feel it on the glass also. Thanks for the suggestion. I'm waiting another year on the next release. I had the iPad 3 prior so the Air 1 is still a nice improvement.