Interesting article at http://www.washingtonpost.com/wp-srv/special/local/dc-shot-spotter/
The map gives you a good idea of places in DC that you shouldn’t be going to late at night.
I would like to see the gunshot data broken down by year. There is also the issue of where the shot spotter sensors are located in DC.
I have a feeling the sensors are heavily concentrated in the eastern half of the city.
Locating the sound
The sound of a gunshot can travel up to two miles, more than enough distance to register on several synchronized sensors. In D.C., an average of eight or nine sensors pick up each shot.
Each sensor records the time it detects a shot. Using the times and distances between pairs of sensors, the system creates curves. The system says the shot was fired where the curves intersect.
Diagram is schematic
Replay animation
Things that can interfere with the system
Alleys
Tall buildings cause sound to bounce around so much that it loses energy and may travel only a few hundred feet. And because sound bends in an arc, a sensor on top of the nearest building may not even pick it up.
Cars
If a person fires into a car and the barrel of a gun is near or within it, the sound is contained and it qualifies as an indoor shot, something the system can’t accurately detect.
Bodies
The sound wave from a shot fired at very close range — within a foot or so — is largely absorbed by the soft tissue of a person’s body and drastically muffled.