Hey there Becca. A couple of questions...have you made his environment too quiet during naptime/waketime? Have you varied his location during naps (in pack 'n play in family room, in car, in stroller at mall, etc.)? Are you at home most of the time where you can control the amount of stimulus? If so, I would encourage you to do some of the following to get your sweet baby used to a variety of sounds:
- have him nap/play in the family room with the TV or music on.
- run the vacuum cleaner in his room while he is napping.
- make some of the noises that seem to disturb him the most on a regular basis (sneezing, coughing, etc.) so that he becomes more used to them.
- take him to the mall, grocery store, etc. where he will be exposed to a lot of different sounds/volumes so he can learn to deal with them.
As long as there is nothing physically wrong with his ears (have his ears been looked at by a dr.?), then it's just a matter of acclimating him to the richness of the sounds of this world.
I have 5 children and 2 of them were quite sensitive to sound as infants. I found that working with them, letting them know they were safe when they heard a noise that scared them and letting them deal with it on their own a little worked wonders. If you silence their world so they don't "melt", they will never learn how to handle it, which could lead to even more significant issues in the future.
I wish you the best! Warmly - J.