I have to agree that the noises are what is getting to him. His sense of hearing is also more acute than ours is. My last girl Morgaine had a complete "eat through the wall, the kitchen counter, part of the bookcase and the case clock hanging 5' up on the wall" meltdown for a week a few years ago when a neighbor was knocking two apartments together. I didn't know that the construction work was being done but I knew she had a complete meltdown for a reason. I stayed home the following Monday to see if there were any new or unusual noises that were upsetting her, that is how I learned about the noise. It was bad enough to really bother me so it was clear why she was so upset. Unfortunately, the work had to go on so I got her a much better dog walker immediately (the one she had wasn't keeping her out more than 10 minutes even though I paid for more) who worked with her to be sure she was calm before she left her alone, and I invested in a DAP plug-in. The combination of the two worked wonders for her.
I hope your boy feels better soon.