Ask anyone who knows me: Draw a line from shoulder to shoulder, extend it out to infinity, I'm pretty much "deaf" for the 180 degree area behind that line - even to other umpires who happen to watch my game.
Only time I ever address a situation WRT rowdy fans is if I hear a threat towards me or other players. Otherwise, hell, I've heard it all, and couldn't care less. Most of them are pretty clueless, so I simply take pity on them. But hey, ignorance is bliss, I guess.