Sensors Tested as Weapon in Cities’ War on Gunfire

Tony Burrola lives in a small clapboard house across from a tidy, tree-lined park. His neighborhood looks pleasant enough, but appearances can deceive. At night, gunfire rattles through the streets, a distressing symbol of the eroding suburban peace in this city beside San Francisco Bay.

“I grew up with this stuff in East L.A., and I moved here to get away from it,” Burrola said. “But it followed me. Those shots, the gang battles in the middle of the night, they scare my little niece half to death.”

Like authorities elsewhere, Redwood City police have tried innumerable tactics to deter and catch those who fire guns at will. Now they think they have found an answer--one that experts say holds immense promise for crime fighters in Los Angeles and the rest of urban America.

Last month, officials here conducted the first tests of a system that uses acoustic sensors--fancy microphones--to detect gunfire in the streets. Mounted atop buildings and utility poles, the sensors record the gunshots and immediately relay a signal alerting police to their locations. In some environments, such sensors can pinpoint the source of gunfire within 20 feet.

Buoyed by the test results, police here are calling the system a breakthrough with tremendous potential. At a minimum, they say, it will dramatically reduce their response time to crime scenes, meaning quicker aid for victims and a far greater likelihood of arrests.

Under current conditions, police must wait--or hope--for a neighbor to report hearing gunfire, and then, once on the scene, struggle to track down its source. In the elapsing hours, witnesses disperse--or grow wary--and the suspect is often long gone.

With the microphones, a gunshot’s location would be displayed instantly on a computerized map at police headquarters, allowing a dispatcher to quickly deploy a patrol car. Some sensors can also distinguish between handgun and automatic weapons fire, giving police valuable tactical information before they arrive.

“If this works like it should, we’ll be advancing light-years in terms of our available law enforcement tools,” said Sgt. Frank Wilkins, the program’s coordinator for the Redwood City Police Department. “Every big city has a problem with random gunfire. In some places, it’s like the Wild West with gangs just running amok. This technology could make a huge difference.”

While Redwood City is the first community to install and test such sensors--in this case made by a Bay Area company called Trilon Technology--the concept of gunfire detection has attracted attention nationwide. Earlier this year, the research arm of the Department of Defense awarded a $1.7-million contract to another company to perfect a sensor system. That system, dubbed SECURES and created by Alliant Techsystems, is scheduled to be tested in Washington or another large city next year.

“There’s a lot of interest in our work,” said Bill Labuda, manager of the sensor project at Alliant, an aerospace and defense firm based in Hopkins, Minn. Their project next year, he added, is a spinoff of Alliant’s work in acoustics related to anti-submarine warfare. It is backed by the National Institute of Justice, which serves as a clearinghouse for transferring military technology to civilian police.

Sensor systems would seem particularly appealing for cities such as Los Angeles, where drive-by shootings and other random attacks often claim lives. Experts said the microphones--and the system’s ability to pinpoint the location and time that a gun is fired--could be a deterrent, making shooters pause before letting bullets fly.

If the system is proved scientifically foolproof, it also might be useful in court, helping prosecutors win convictions in cases in which other evidence is lacking.

Although there has been no organized opposition to the sensor system, some residents are likely to have qualms about living in the midst of concealed microphones monitored by police 24 hours a day.

“There is a certain wariness in some neighborhoods about police presence and activity,” Labuda said. Alliant’s sensors do not record human speech, but Labuda conceded that “community endorsement of the system is essential before any project goes forward.”

Another potential roadblock--especially for a sprawling city such as Los Angeles, which covers 469 square miles--is cost. The computer costs are nominal, but the sensors run about $2,000 apiece under the system developed by Alliant. To cover a one-mile-square area, police would need about 100 microphones, company officials said.

“The cost really depends on the size of the area to be covered,” Labuda said. “The key is to target your problem areas and focus on them.”

In Redwood City, population 69,900, the gunfire problem has been mushrooming for several years. While there have been no recent deaths related to random shots, gun battles among street gangs are common, and celebratory shooting--particularly on holidays, when revelers fire weapons toward the bay--is rampant.

“We have one neighborhood near the water where the residents leave town over New Year’s because of the shooting and come back to find their homes riddled with bullet holes,” Wilkins said. “It’s only a matter of time before we have fatalities, because a bullet that goes up will come down with lethal force.”

About a year ago, residents who were fed up with the gunfire pressed officials to act. One mother, Maria Diaz, told the City Council how she takes refuge with her daughter in the bathtub when gunfights rage outside her home.

“You can’t understand what it’s like until you’ve experienced diving [for safety] with a child in hand,” she said. After considerable debate, the council decided to spend $25,000 for initial tests of the gunfire detection system created by Trilon Technology.

Robert Showen is Trilon’s founder. He has been perfecting his acoustic sensors for several years, working out bugs that could cause false readings and other glitches. He has high hopes for the technology.

“We think it’s an idea whose time has come,” Showen said. “One day, I believe this could be as ubiquitous in our country as 911.”

The concept underlying the Redwood City system is simple, resembling the science used to determine the strength and epicenter of earthquakes. Microphones, placed at various locations in the city, receive the sound of a given gunshot at slightly different times. A computer analyzes the differences in times, then calculates the shot’s location.

One challenge, scientists say, has been designing a system that accounts for obstacles, such as buildings, that interrupt the travel of sound. Also difficult is equipping the computer to distinguish between gunfire and other loud city noises, such as jackhammers, backfiring cars, blaring horns and even the wind.

Just before Christmas, police conducted the first test of the system in a one-square-mile section of southeast Redwood City, an area plagued by gunfire. First, technicians mounted five microphones atop a church, two apartment buildings and other structures in the test area.

Then, while Trilon officials monitored the computer at police headquarters, police officers fired blanks into the air at seven locations in the test zone. Though residents were warned about the test, the nighttime shooting brought many residents to their windows and prompted a flood of calls to police. The shots also triggered car alarms and prompted dogs’ barking.

Despite such side effects, the test was proclaimed a success. The shots were properly recorded by the microphones, and their locations were identified within seconds. More tests are scheduled this month--this time for real gunfire.