Covering his ears.

I have noticed lately that sound seems to be bothering him a great deal.
We can not complete an activity without him commenting on a sound that is distracting him or the act of covering his ears with his hands. Its as if he can not filter out all the noise that is going on around him while he is trying to do work.
I try and think what he must be hearing, is it louder than what we hear it at? is it too much at once? all at the same level of loudness? What is the noise that he hates so much?
We have used the headphones a number of times lately and these seem to be doing the trick, if Thomas is annoying him ie, just being in the same room. He can put the headphones on and make it go away.