I have a junction box in my unfinished attic that supports a light fixture in the room below. It doesn't fit exactly to the lath and plaster and I'd like to insulate for sound intrusion (the attic is well insulated so I'm not worried about temperature).
You can buy recessed lighting insulators like the one in the picture, but they're $15 and way too big. These are 2x4 joists and I'd like to put some plywood down so there's not a lot of headroom to work with.
I can spray foam and caulk all of the holes but that seems like a hassle and an opportunity to make a giant mess. Is there a better way?