when I had mine done I was told this reaction is a combination of dissociation and clausterphobia. The repetative loud noise and the closeness of it caused me to space off and anxiety. So I got the same reaction that I do with my Dissociative Identity disorder and with my anxiety panic attacks - as if I had dissociated completely into my la la land and come back one huge headache and blurry eyed and so on and not being able to breath and panicky feeling. The feeling passed after a bit.