They Can Hear You Now...

J.A. Terranson measl at
Tue Jul 5 19:42:33 PDT 2005

CHICAGO, Illinois (AP) -- Police installed video surveillance cameras
around town and saw Chicago's murder rate fall to its lowest level in four
decades. Now the cops hope to further cut crime by not only watching, but
listening, too.

The city is employing 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.

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 of Safety Dynamics LLC, the
company in suburban Oak Brook that makes the systems.

The technology isn't just gaining favor in Chicago, where 30 of the
devices have already been installed in high-crime neighborhoods alongside
video surveillance cameras. Baker says dozens more installations will

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, Pennsylvania, and San
Francisco, California, are close to launching test programs of their own,
and New Orleans, Louisiana, and Atlanta, Georgia, also have made
Military use

Safety Dynamics also works with the U.S. Army and Navy, developing systems
that could detect a range of sounds such as glass shattering or diesel
trucks slowing in an unexpected location.

Some U.S. troops in Iraq already have a similar system that works
differently. Designed quickly in late 2003 and early 2004 by the Defense
Advanced Research Projects Agency and BBN Technologies Inc. of Cambridge,
Massachusetts, a detector known as "Boomerang" can be mounted on the back
of a moving vehicle to locate hostile gunfire.

The Safety Dynamics system deployed in Chicago, known formally as Smart
Sensor Enabled Neural Threat Recognition and Identification -- or SENTRI
-- uses four microphones to triangulate, or zero in, on the shooter.

By contrast, the Boomerang has sensors mounted atop a pole that detect
shock and sound waves from a muzzle blast.

In Chicago, police hope the SENTRI system 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."
Privacy matters

The American Civil Liberties Union in Illinois is concerned about privacy
rights being violated by the city's prevalent camera system. 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.

As long as the cameras and SENTRI system are set up in public spaces, they
do not violate the law, said Northwestern University Law School 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 say 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 SENTRI is programmed to recognize only gunshots, not
record conversations or "bug" private homes.

"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.

Each SENTRI contains a library of acoustical patterns, or "sound
signatures," which Berger developed over several years. They're used to
differentiate gunshots from other noises, such as traffic and
construction, by measuring the unique decibel level of a bullet being
fired. That way, a gunshot activates the system but a car backfiring does

Adding SENTRI to an existing surveillance camera is not cheap, however.
The system costs between $4,000 and $10,000 per unit. In Chicago, money
forfeited by criminals is used to pay for both it and the accompanying

As a result, Police Superintendent Phil Cline told a recent U.S.
Conference of Mayors meeting, "the drug dealers are actually paying to
surveil themselves."

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