I am so sorry, that sounds awful. It is hard for me to hear it all day and I have the ability to change conditions in the playroom to settle them down at any time. I don't know how I'd handle it if I could not quiet it down at will.
Family childcare is protected, so as long as the landlord is OK with it, there is not much that can be done. It is not the answer you were hoping for and it would not be one I would take easily, either.
You can control your space, though.
Have you tried sound machines on that side of the building? Large, deep-toned windchimes on the porches? I know it sounds crazy, but my neighborhood often has gunshots, glasspacks & bass speakers driving by and large machinery noise during naptime; it has really helped.
