too loud!

What do you do with someone who plays music SO loudly that their earphones are pulsing out of their ears, the entire room can hear the thump, thump, thump and he doesn't seem to notice?? I guess wait for someone else to say something.  While sometimes I can make the approach (like when the woman on the greyhound bus had her seat SO reclined, I was staring at her scalp), often I don't say a peep because I just don't want to seem rude.  But why?? He's the one being so disrespectful of the others trying to work.  Hmpf.  Hopefully my soft tunes will drown the base away...

Also, someone seems to have had a loud rant in the library.  Started off by yelling "help, help, help" which got the library guards to go running and is now yelling something about racism.  Oh boy.

Now that the screaming woman has stopped...can some kind person tap this rude gentleman on the shoulder and tell him to CUT DOWN HIS MUSIC?!  

If the music is too loud in the library - shhhhhhhhhh!