"Loud" is unfortunately hard to quantify. There's a lot of psychoacoustics that mean that the number of decidels really doesn't tell you what's loud and what's not.

This is a great demo of how sounds can appear extremely loud without actually being physically very loud: https://youtu.be/tONF9OSUOSw?t=7m16s

Anyway the point is that it's hard to make rules about this kind of thing, because sound is subjective and there are ways to circumvent any restrictions you make.