I’ve read several dozen comments, but I haven’t come across the following stated quite this way:
One option is to politely ask someone if they have headphones and/or to turn it down.
Cont’d from ^: you can often lubricate the situation by giving some “reason” that lets the other person save face. You can be genuine or creative or both. (You might say you just really had a rough day and would appreciate quiet.)
As a point of comparison, think about how many drivers forget to turn on their headlights even after the sun goes down. Some fraction of people screw up in spite of their self-interest.
If you are genuinely afraid of speaking to someone, listen to your gut. Just try to check this against reality… if this happens at 1000X the rate of crime in the area, you might be miscalibrated.
You might consider talking to Mr Blaring McLoud without mentioning your annoyance at first. This might help get you one step closer to asking nicely later.
Some people are genuinely unaware, so erring on the side of kindness is a smart step one. Even when asking nicely without snark or impugning someone’s pride, you might still face rude behavior. I like the phrase “don’t mistake kindness for weakness.” You can walk away and figure out what you want to do next, knowing that you gave the other person a chance.