Most police sirens have a very distinct wail that frightens criminals, stresses speeders, and annoys the hell out of anyone who lives near a precinct. Yet every cop car in New York sounds like a different IDM DJ trying to mess with your ears. Despite this being arguably the most in-your-face city in the world, its sirens usually aren't intrusive enough to get people out of the way. I propose they be changed to something more alarming.
The sound of someone vomiting
-Loud, guttural heaves should certainly get people uncomfortable and quickly onto the sidewalk. Hearing this as I cross the street would stop me in my tracks and check my clothes for stomach matter.
The whistle of a bomb dropping
-You know the classic sound. It might have been more effective to use this directly following 9/11, but it should still get people moving. I think it would be more menacing to hear the constant whistle without ever hearing the explosion, but I might be wrong.
Police officers calling people out
-Hearing actual officers getting personal with those in their way would strike fear in those not wanting to be ridiculed. Just imagine a cop yelling, "Hey tall guy with steel wool for hair, people are gonna die 'cause you won't get your hipster ass out of our way!" I certainly wouldn't want to hear it.
A baby crying
-Having been on many flights, the one thing that still irritates me is the incessant cry of a hungry, gassy baby. The shrill siren screams would have pedestrians covering their ears and running for silence and drivers pulling off the road and turning up their stereos.
Audio from an episode of Mind of Mencia
-You know he's annoying when even Maxim rates him as the 12th worst comedian of all time. Hearing one or two “DEE-Dee-dee's” would drive me insane. Throw in completely offensive jokes about midgets, the handicapped, and homosexuals and I would never want to see a cop car again. Maybe they'll even toss in one of his ridiculously self-righteous quotes:
"Somewhere right now, there is a soldier dying to protect our rights. One of these rights is free speech. And I will never let a soldier die in vain."