AP Photo/Charles Rex Arbogast

A Chicago Police Department surveillance camera is seen mounted on a light pole Tuesday, June 14, 2005, on the city's South Side. The black spider-like device mounted above the camera is a Smart Sensor Enabled Neural Threat Recogniton and Identification,

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."