Park police department suggesting ways to help the police by means of gunshot location systems. The police chief arranged a meeting with local inventors and entrepreneurs who had expressed an interest in the problem. At that time there were no solutions to tracking gunshots, only a desire to do so. One key attendee was Robert Showen, a Stanford Research Institute employee and expert in acoustics. Lahr decided to go ahead with his plans to demonstrate the feasibility of locating the gunshots, relying on his background in the earthquake location techniques and monitoring in Alaska. A network consisting of one wired and four radio-telemetered microphones was established, with his home in eastern Menlo Park becoming the command center. Lahr modified the software typically used for locating earthquakes and recorded the data at a higher sample rate than is used for regional seismology. After gunshots were heard, Lahr would determine their location while his wife monitored the police radio for independent confirmation of their source. Using this system, Lahr was able to demonstrate to the police and others that this technique was highly effective, as the system was able to locate gunshots occurring within the array to within a few tens of meters. Although additional techniques from the seismic world were known that could better automate the system and increase its reliability, those improvements were outside the scope of this feasibility study. Gunfire characteristics There are three primary attributes that characterize gunfire and hence enable the detection and location of gunfire and similar weapon discharges: An optical flash that occurs when an explosive charge is ignited to propel a projectile from the chamber of the weapon A typical muzzle blast generates an impulse sound wave with a sound pressure level (SPL) that ranges from 120 dB to 160 dB A shock wave that occurs as a projectile moves through the air at supersonic speed. Note, this does not apply to subsonic ammunition, whose bullet projectiles do not exceed 1120 feet per second (i.e. the speed of sound in air). Optical flashes can be detected using optical and/or infrared sensing techniques; however there must be a line of sight from the sensor to the weapon, otherwise the flash will not be seen. Indirect flashes that bounce off nearby structures such as walls, trees, and rocks assist in exposing concealed or limited line-of-sight detections between the weapon and the sensor. Because only optical flashes