I wonder could you experiment with additional white noise machines? I have had similar troubles in the past, and my therapist put in a couple of machines- one outside the door so I feel less likely to be heard, and another one in the office so I don't hear other people. That solved the problem for me but I wonder is there anything else you might try- you can get a white noise app if you have a smartphone so maybe having that really close to you would help as well? Just a thought.

I found it very disturbing to hear other people, so I relate. I would keep complaining about it until I was happy with the situation. I think it's a really big deal if it bothers you.