Also in parks please (at least in the US). I’ve noticed an increasing trend of mostly young people blasting their unwanted music through loud speakers at peaceful parks, ruining the experience for everyone else.

Ah yes. Blind Faith's inaugural free concert in Hyde Park. Ginger Baker, Eric Clapton, Rick Grech, Stevie Windwood. I remember it to this day.

Living in a place where a lot of people does this, I'm all for it. Even more, ban people doing their "walkie-talkie" conversations on Whatsapp in loud voice.

I am all for total ban of loud music. If it leaves your car, office, place of work or home it should be prosecuted.

Same for dog barking.

Forget cones of shame, what we need are cones of silence.

Most public places (cafes, stores, etc..) have music playing. Why not public transit?

There's a famous album called "Music for Airports". There's a genre called "Elevator Music". Why shouldn't there be "Music for Public Transit" or "Public Transit Music"?

This would lead to extremely racist-looking enforcement, and therefore even if passed it won't be enforced.

No, public transit does not have to be an inherently noisy place. It's the people playing loud music causing that to a large degree, and they need to be removed.

I've ridden a LOT of public transit in my life, and loud music was not even top 10 things that cause noise pollution. Crying babies, people taking phone calls, honking horns, large trucks, rails squealing. But sure, I guess if you've solved all of those, loud music might annoy.