I mean I agreed with you I just dont know how to do that without interacting. Thats how norms are shifted.

The other day I was in a store and there was 2 old guys looking at sunglasses, one of the was messy coughing all over the place and trying on the sunglasses, putting them back on the shelf covered in his gunk. Workers kind of looking on cautiously keeping their distance. Guys were having a good time chatting with each other and joking. I caught his eye and said "that is gross, put on a mask or something" in a normal volume/tone. Not the most eloquent but it got the point across. And they stopped joking and looked at each other, taken aback and their fun moment ruined. Then I left as my business was concluded anyway. No big scene, just a reminder for them that there are other people around. And if you are with your buddy having a good time, its more conducive to the atmosphere to not be snottering all over the place. They were not bad people they were just carried away in their little comfy bubble that feels like home to them.

People have done interventions like that on me in my life and I remembered them. Generally it is a shock so you don't necessarily adjust right away but after I had time to think about it, I eventually did on subsequent occasions.

But dont discount the value of dirty looks, mumbling to yourself, or subtle gestures. Maybe you can just go to another part of the bus. Most people won't like the feeling that they are being shunned by strangers. Or get a white noise app to turn on when needed. That would be funny? Or ask if they would take a request from you next song. A joke is less confrontational but can clearly communicate.

But you will have to engage in an uncomfortable human interaction in order to contribute to the shift in social norms. Either you Iearn to ignore, avoid/exit the situation, or take the risk of unknown outcome by challenging in some way. People do this all the time and it rarely leads to fights. Its part of living in an urban environment. We are in tension with each other all the time and its OK. Nicer than feeling murderous every day.