I had this not long ago sitting in 1A on a 747, with the pax in 1K playing a video on his phone using the speaker. It was pre-take off and not terribly loud - although still loud enough to be irritating - and I took a calculated gamble that it would stop when the flight began, as it did. So no need for pro-active intervention, but what possesses someone on F ever to behave like this ?

However, all in all it ranks quite low in the annals of anti-social in-flight behaviour ....