Android smartphones can do a wide variety of things, including helming space missions. And now researchers have developed a new Android-based device that can potentially help users and law-enforcement agencies solve violent crimes.

Computer engineers from Vanderbilt University's Institute of Software Integrated Systems have found a way to track gunfire using smartphones. The team made this possible by developing an inexpensive hardware module for the phone and related software that transformed it from a generic Android smartphone into a simple shooter location system.

Where's the shooter?

Where's the shooter?

Almost all firearms in the world produce unique sonic signatures when they are fired. This is the basis of the software that is at the heart of this development. The sonic signature is largely a product of two sounds. The muzzle blast spreads out from the muzzle each time a gun is fired; it then expands as it moves further away from the point of origin. Bullets travelling at supersonic velocities also produce distinctive shockwaves as they cut through the air. A system that combines an array of sensitive microphones, a precise clock and an off-the-shelf microprocessor can detect these sounds and match them to a signature. The signature can then be used to pinpoint the origin of the gunfire with a great deal of accuracy.

Of course, such devices have been used by armed forces around the world, but implementing it in a smartphone makes it more mainstream and, some would argue, more mainstream than it needs to be. For the system to work at its most effective, several nodes or devices are needed in order to pinpoint a shooter's location. So naturally, this technology is best suited for agencies with larger resources than individuals.

Besides the smartphone, the system consists of an external sensor module that houses the microphones and the extra processor for detecting acoustic signature. The module logs the time of gunshots and sends the information to a smartphone over a Bluetooth connection. Data on a smartphone can then be send to other modules, which eventually gives you the origin of the gunshot by a simple triangulation method.

There are two versions of the module. One has a single microphone and gauges both the muzzle blast and bullet shockwave, but requires six modules to obtain accurate locations. The other option is a slightly larger module, which houses four microphones and relies only on the shockwave data. Only two modules of this kind are enough to accurately pinpoint the direction of the shot, with a rough estimate of the range.

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