The problem is you have to quantify and then accurately measure "normal volume" and also clearly state exactly what constitutes an "annoying" noise and then if you do it opens up ways to maliciously comply.

If you set the volume limits at x dB then can me and 5 of my mates each play 6 different dubstep songs at the same time below or exactly at the volume threshold? Is it OK for loud ringtones? Will there be a time limit to account for ringtones? If so, can I play whatever I want loudly as long as it adheres to the time limit?

If the law is too vague it will be either impossible to implement or overreaching.

I have personally ran into a few proper cunts of stewards or municipal police officers that just like to harass people and then give them a fine when they inevitably react. This sort of law is always used to oppress more than it's used to make everyone's life better.