This is a problem for our time: I was recently in a coffee shop when I noticed a person seated a few feet from me using his mobile phone to listen to recorded content while not using headphones.
It was unpleasant, especially when combined with the pre-recorded music playing in the background and other in-person talks.
After a while,
I inquired, "Sir, do you chance to have earphones or headphones that you could use?" in a very nice and civil manner.
I praised him for simply turning the device off after he bristled somewhat and said he didn't realise the noise was bothersome.
Is my behaviour appropriate and polite in this situation?
However, I believe that playing anything loud enough for someone else to hear amounts to forcing your decision on them and is therefore impolite.