CHICAGO -- The police are watching. And in Chicago, they're listening, too.
City officials are using new technology that recognizes the sound of a gunshot within a two-block radius, pinpoints the source, turns a surveillance camera toward the shooter and places a 911 call. Officials can then track the shooter and dispatch officers to the scene.
Welcome to crime-fighting in the 21st century.
"Instead of just having eyes, you have the advantage of both eyes and ears," said Bryan Baker, chief executive officer of Safety Dynamics in Oak Brook, which makes the systems.
After a successful pilot program, Chicago officials have installed 30 of the devices alongside video surveillance cameras in high-crime neighborhoods, with 12 more on the way, and dozens more to follow, Baker said.
The system's formal name is Smart Sensor Enabled Neural Threat Recognition and Identification - or SENTRI. And the technology is not just gaining favor in Chicago.
In Los Angeles County, the sheriff's department plans to deploy 20 units in a pilot test, and officials in Tijuana, Mexico, recently bought 353 units, Baker said. Police in Philadelphia and San Francisco are close to launching test programs of their own, and New Orleans and Atlanta have also made inquiries.
Safety Dynamics also works with the U.S. Army and Navy, developing projects that could detect a range of sounds like diesel trucks slowing in an unexpected location or breaking glass, Baker said. On Tuesday, a military contractor in Iraq responsible for detecting explosive devices contacted the company about mounting systems on vehicles that carry U.S. military personnel.
"They want to put 20 of them on Humvees to be able to detect gunshots," Baker said. "The soldiers, they're getting shot at, but they don't know where the shots are coming from."
In Chicago, police hope the gunshot detection systems will add momentum to a technology-fueled crackdown on guns and gang violence. The city in 2004 reduced its homicide rate to its lowest level since 1965 and police seized 10,000 guns - successes that were in large part credited to a network of "pods," or remote-controlled cameras that can rotate 360 degrees and feed video directly to squad-car laptops. The SENTRI systems are an addition to that network.
"They have been extremely successful," said Monique Bond, spokeswoman for the Chicago Office of Emergency Management. "We've been able to see the benefits that cameras and advanced technology bring to the community."
The American Civil Liberties Union in Illinois said it is somewhat concerned about privacy rights being violated because the city's camera system is so prevalent.
Spokesman Ed Yohnka said officers need to be properly trained in monitoring the cameras and only record activity in public spaces, such as sidewalks and streets.
"That it could someday gravitate toward the violation of individual rights, that applies no matter what system it is, including these," Yohnka said of the pods with the sound detection systems.
As long as the cameras and SENTRI system are set up in public spaces, they do not violate the law, said Northwestern University School of Law professor Robert W. Bennett.
"You don't have much in the way of privacy issues when you're in a public area," Bennett said.
And local officials said it's hard to argue with the results.
"The crime rates in Chicago are the lowest in 40 years. The price of keeping the community safe far outweighs civil liberty issues," Bond said.
Baker stresses that Chicago SENTRI are only programmed to recognize gunshots, not record conversations or "bug" private homes.
"The microphones can't be used for listening, there's no mechanism for other sounds like human voices," he said.
SENTRI is the brainchild of Safety Dynamics and Dr. Theodore Berger, director of the Center for Neural Engineering at the University of Southern California in Los Angeles.
Each SENTRI contains a library of acoustical patterns, or "sound signatures," which Berger developed over several years.
Four microphones in the system differentiate gunshots from other noises like traffic and construction by measuring the unique decibel level of a bullet being shot out of a gun, and comparing the sound to its library. That way, a gunshot would activate the system, but a siren or a car backfiring would not, Baker said.
"We take recordings of the target sound and you take as many different recordings as you can from as many different types of scenarios as you can," he said. "But it's a little bit like fingerprinting. The more precise the sound we get, the greater the possibility that we eliminate some potential gunshots."
Adding the SENTRI to an existing surveillance camera is not cheap. The system costs between $4,000 and $10,000 per unit, but in Chicago they and the accompanying cameras are paid for with forfeiture money.
Police Superintendent Phil Cline told an audience at a recent U.S. Conference of Mayors meeting, "the drug dealers are actually paying to surveil themselves."
