SENTRI surveillance

A microphone surveillance system based on brain cell research is being used to combat shootings on the streets of Chicago and Los Angeles. The SENTRI system developed by Theodore Berger, director of the University Southern California's (USC) Center for Neural Engineering, has been trained to instantly recognise the sound of a gunshot within a two-block radius with high accuracy. SENTRI can then tag where the shot was fired, zoom in and photograph the shooter with it's built in camera and even make a 911 call to the police station. Police can then remotely control the camera to track the offender and dispatch officers to the scene in an integrated human-computer crime response.

Berger, who is also a key researcher in the USC Viterbi School of Engineering's Biomimetic MicroElectronic Systems Engineering Research Center, has pioneered SENTRI by deciphering the way in which nerve cells code messages to each other. SENTRI was then built by an Oak Brook, Ill.-based firm named Safety Dynamics, a company in which Berger serves as chief scientist. SENTRI uses acoustic recognizers, posted in trios or larger groupings on utility poles or other listening posts, which are tuned to certain specific warning sounds with extremely high accuracy.

"A simple loud noise, even an explosive noise, won't set them off," Berger said.

The device is listening for the entire sound pattern of the gunshot, not just the initial explosion, which makes it much less likely to mistake other loud noises for shooting. A specially configured computer system (a "directional analyser") accurately calculates any authenticated gunshot's location - using the difference in the time the sound arrives at the different microphones on a SENTRI acoustic unit.

Field tests with real weapons have shown 95 percent accuracy with respect to gunshot recognition, and 100 percent accuracy with respect to centering an attached camera on the shooter for those recognized gunshots.

SENTRI is an acronym for "Smart Sensor Enabled Neural Threat Recognition and Identification." The "neural" in the title refers directly to Berger's work, which was based on analysis of the "language" nerve cells, or neurons, use to convey information, and specifically on his modeling of the way the brain forms memories of sounds. The neurons' only way of distinguishing signals is to fire repeatedly, either faster or slower, in different temporal patterns.

"It is the time difference between pulses that carries the information," Berger said. "This is a coding completely unlike that used by computers, which are collections of ones and zeros, changing to the beat of a constant clock."

The SENTRI system has been incorporated into a Chicago based test in concert with a major police department, who are including Safety Dynamics gunshot recognition and directionality in the next phase scheduled for deployment at the end of 2004. The original strategy for the camera systems was as a force multiplier and crime deterrence program. Safety Dynamics was not involved with the camera deployment, but it proved highly successful for the neighbourhoods. In the next phase, the gun shot recognition, locator, and camera control information are installed and will provide the police command center with an instant notification, location of the gunshot, and immediate live video feed from of the area where the gunshot occurred even amidst high noise.

Other potential uses for the SENTRI system include protecting oil pipeline security, including diesel truck identification, forest protection with chainsaw activity detection, and securing of facilities and perimeters including sensitive sounds like chain link fence climbing and cutting and other human noises.

For more information: http://www.safetydynamics.net