The system, ShotSpotter, is in use in many cities, and this investigation shows how such urban data can be used.
"In recordings played for reporters Thursday, the plane's two engines can be heard clearly. Some of the sensors caught the sound of two loud bangs, apparently when parts of the plane, including a wing, an engine and the landing gear, hit buildings and vehicles on the ground.
In one chilling recording, screams of people witnessing the crash can be heard.
The sensors 'picked up probably critical portions of the crash itself and the events leading up to it,' said Police Chief Ron Davis. 'It is a very clear and, quite frankly, powerful tape of the events.'"