I am trying to find data that reports the decibel level at NBA games. I prefer as granular as possible - minute-by-minute would be fantastic.
This is an incredibly specific data request -- I don't think there's any chance of just finding this in the wild. Your best bet is probably to obtain TV recordings of NBA (either record them yourself or hunt around online) and analyze the decibel levels in audio track yourself. Of course, this has a few issues: you'll have to cut out commercial breaks/instant replays/etc, you'll have to somehow filter out the commentators or something (the commentators' volume should be consistent on average over the course of the game, so this should be feasible, if not ideal), etc.
That's a lot of work and it won't produce the most accurate results, but I think that's the best you're going to get in the realm of open data.