This happened last year on a long-distance bus from Beijing to Tianjin, which takes about two hours. I was travelling to visit my parents after a very long week at work, and I was looking forward to sleeping on the way.
The person was a man in his thirties sitting directly behind me. As soon as the bus left, he started a video call on his phone on speaker, at full volume. For the first ten minutes I assumed he'd stop soon. He didn't. He talked loudly for about an hour, and then, when the call ended, he started watching videos, again without headphones. On top of that, he kept pushing his knees into the back of my seat.
I eventually turned round and politely asked if he could use earphones. He looked surprised, said he didn't have any, and carried on. A few other passengers rolled their eyes, but nobody said anything, and the driver didn't seem to notice.
I think it annoyed me so much for a few reasons. The most obvious was that I was exhausted and couldn't rest. But more than that, it was the lack of consideration. A bus is a shared space, and he behaved as though he was in his own living room. What also frustrated me was that nobody else spoke up, so I felt like the difficult one. Looking back, I probably could have asked the driver for help. It also made me more aware of my own behaviour; I now always carry spare earphones, partly to make sure I never become that person.