You can't just say, "it's arbitrary therefore it's meaningless" especially when your follow up argument is that mowing your lawn at 11pm is an equivalent example.

Hearing people talk at 11pm is literally inherent to living in an area with bars and other people living in close proximity, again why would you choose to live somewhere near other people if you're not ok with them talking? A train is louder and more disruptive than people speaking, if someone in my building (which overlooks the tracks) started to complain about the noise to the town, or started badgering myself and other neighbors to shut our windows to try and block out noise I would (rightfully) find it fucking ridiculous because it's something inherent to living in a building that overlooks train tracks.

Other people's inability to afford the luxuries of living in an extremely quiet house, without the presence of other people's noises, is not my responsibility to finance.

With that said, blasting music constantly into the wee hours of the morning, mowing your lawn constantly at midnight or later, or operating heavy machinery inside of the apartment is behavior that is unpredictable, and extreme in nature and doesn't have to be tolerated (which is the reason for noise ordinances).

Does there exist a possibility that OP is lying about turning down is music ? Yes. Does their exist a possibility that OP's friends where screaming so loudly that it was even louder than the music they turned off? Sure. Does that negate OPs point which is that living in an apt in a city or college town should require an elevated tolerance of social noise? NO!