Occasionally I'll ask people to quiet down, but I'm usually polite. I figure if I've got headphones on & they're so loud they're interfering w/ me actually listening to the movie, etc, they're a bit 'too' loud.

Normally what I do is go to the bathroom (was going anyway) & lean over a bit & say very quietly to them, btw - "I'm not sure you realize, but your voice is carrying a bit far & is interfering a bit w/ movie/sleep, etc. Could you just bring the level down a bit?"

Most don't realize it & say oh we're so sorry. Others (figuratively) flip you the bird, in which case I have no problem w/ going to the FA & saying (nicely) they're loud, I politely asked them to tone it down a bit, I (and everyone else) would like to sleep/do movie, etc - would you please take care of it. The FA usually does then. And I don't care if the loud folk don't like it.

What amazed me one time was how much someone who brought his own (HUGE) bag of potato chips & other stuff in a grocery bag made so much noise rattling the d*mn chips bag while he scarfed down. That happened to me 2 times (2 dif folk on 2 dif flights) & for the first time ever I understood road rage. I literally wanted to beat the crap out of that guy, but figured I'd be the one taken off the plane.

BTW - seat back & loud voices are not sequential - not relevent - don't try to confuse 2 separate issues.

Cheers.