ETIQUETTE QUESTION

How can we explain to people, especially people in airport waiting areas, that they don't have to raise their voices when they talk on their cell phones? Seriously, HOW CAN WE MAKE THEM UNDERSTAND THIS?? Take, for example, the guy sitting next to me this morning, whose name was Roger, and who was telling somebody on this phone that somebody named DeeDee had REALLY SCREWED UP HIS TRAVEL ARRANGEMENTS, REALLY SCREWED THEM UP, BUT HE WAS IN MIAMI NOW AND THE WEATHER WAS A LOT NICER HERE THAN IN DETROIT HA HA HA HA! BUT DEEDEE REALLY (CLONK)

In my imagination, I just hit Roger on the head with a baseball bat. But we can't do that for real, because (a) it would be wrong, and (b) you can't get a bat through security.

Probably the simplest, and safest, answer would be some kind of system involving highly trained snipers.