The neighbor’s teenage son is driving my wife crazy

I’m really worried about my wife. The 18 year old plays music loud, and we share a wall, so sound travels very easily between the two houses. She has misophonia and the base really drives her up the wall. I mean, anxiety so bad it’s making her physically ill. We’re trying different methods to help her cope (different ear plugs, going to talk to a doctor) but it’s not like we can really express to this kid how badly it’s affecting her mental health to be so on edge all the time. We’ve talked to his mother a few times and she’s gotten him to turn it down to a reasonable level, but they’re away right now with their other two youngest (don’t ask me why they didn’t take him, I wish I knew) and so, naturally, he’s playing music at the volume he likes.

I want to march over there and demand he start using headphones, but I also don’t want to start anything. And neither does she. We plan to have a talk with the mom when she’s back, but the waiting is agonizing and watching my wife be on the constant cusp of a mental breakdown is so hard to watch. Please, what can I do to help my wife cope with this? I’m so worried for her.

Edit: Naturally the day I make the post, next door decides to come home lol But all the advice I’ve received from everyone has been taken to heart and I greatly appreciate the broader perspective you’ve given me, both harsh and kind. It has been noted and will be used to calmly discuss our difficulties with them going forward. Thank you all (: