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Lititz, PA high school junior creates gunshot detection system that pinpoints shooter location on a map

Shohini Baneerjee, Warwich H.S.

By Karen Ferrick-Roman

Coordinated attacks in a Paris concert hall and cafes. A lone gunman killing nine and himself on a rural community college in Oregon—on an October day when campuses in Arizona and Texas also felt the pain caused by shooters.

These occurrences are close in time but very different threats in very different environments.

Yet an idea, initially designed as a science fair entry by a high school student, could help to pinpoint the location of a gunshot and immediately send notifications in these situations and more. The brainchild of Shohini Banerjee, a 17-year-old 11th-grader at Warwick High School in Lititz, Pa., the system is the result of five months of work by a young person who is driven to make her world better.

“Every time a child is shot or a terrorist attack is unleashed on innocent lives, my heart breaks, over and over,” Banerjee says. “There were 51,727 incidents of gun violence in 2014 in the U.S. alone. This is why simple, yet effective technology to provide immediate response is so crucial. Though it is easy to go into a school or any soft target and shoot people, we can take measures to prevent more lives from being lost, and that is why I want to see my project through.”

The system is built around Raspberry Pi, inexpensive credit-card-sized computer hardware intended for educational purposes and favored by the maker community. The intent is to serve as an early warning system in the instance of an active shooter.

Banerjee created and attached a small microphone and audio circuitry to the Raspberry Pi unit, then created software that turned the tiny computer into a gunshot detector. Connected to the Internet, it can notify authorities, local law enforcement and others within seconds (in the same timeframe it takes a short text email to be sent) of the precise location of the shots, she says.

Banerjee envisions that the simplicity of this system could allow gunshot detectors to be installed with the same frequency as low-cost smoke detectors. “If the cost of a gunshot detector is down to several dollars, you could afford to have lots of them,” she notes.

The prototype cost her about $50 to make from components off the shelf. She anticipates that model priced for mass marketing might be made for $15 or less.

The price stands in stark comparison to existing gunshot detectors, sensitive microphones and systems that have dominated the marketplace. Fusion Network reports that such systems are used in more than 90 cities nationwide, including Brooklyn and the Bronx—where the cost of installation, according to policeone.com, reached $200,000 to $250,000 for a square mile of coverage. In addition, privacy concerns have been raised because of the possibilities of these sensitive microphones picking up personal conversations, reports Fusion Network, and police end up being deployed even though about 75 percent of the calls received are false alarms. The sensitivity of the microphones—as well as the expense of the systems— means that detectors must be placed far apart.

Shohini Banerjee’s system works on a different premise: that with low-cost microphones and computers, the detectors can saturate an area so that someone is never far from a sensor. Each detector can be powered by a standard USB cell phone charger and, via a Wi-Fi dongle, attached to an institution’s existing computer system.

The Internet connection and capability allow the system to email, text or connect to other systems as its alert notification system. At the end of the day it’s just a scaled-down, full-functioning Linux-based computer, Banerjee says.

She developed an algorithm for three such detectors to use multilateration, triangulating the time and place of when they register a loud sound. By tapping into the Internet’s free Network Time Protocol, the detectors determine, to the timing of milliseconds, at which GPS coordinates the shot was fired. By using this information from the detectors in a series, the system pinpoints the location of the shooter on a map which she sends to first responders.

Banerjee tested the detectors at a firing range and has found the system accurate to within 6 to 8 meters (19 to 26 feet), sensitive enough to pinpoint whether a shot came from the back or the front of a bus, for instance.

Not only could the information hone the location, it could help to prevent the escalation of an incident and help authorities decide on the best response.

“You cannot stop the first shot from being fired in a school, courthouse or airport,” Banerjee says. “But, within seconds, people could know whether to lock down or evacuate.”

This type of gunshot detection system, she says, could have applications for military as well as institutional uses. For military use, she explains, the detectors could be attached to drones with GPS systems. “Each microphone will hear the shot at slightly different times. It only takes a fraction of a second to calculate the GPS coordinates of the gun shot, pull up a map and say, ‘This is the building.’”

She again drew on the similarities between smoke detectors and these gunshot detectors as having little drain on both electricity and bandwidth. “It sits there doing nothing all of its lifetime,” she says, “until it saves someone’s life.” 


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