Amplifier? ("Attention. The passenger in seat 28B would appreciate another half a can of Diet Sprite." "Ahem, would the gentleman in about seat 26C please stop passing gas?" "Kid, if kick the back of my seat one more time, I'm going to stuff you in the bathroom that the gentleman in seat 26C just came out of and lock the door.")

More seriously, if it became common knowledge, I can't imagine the kinds of kid and teenager toys that might appear. And how little some parents would care. As if some of those battery-operated things weren't bad enough already ... even with the muffler on you have to endure all that clicking and grunting.