Suresh Venkatasubramanian, University of UtahSound Intelligence CEO Derek van der Vorst said security cameras made by Sweden-based Axis Communications account for 90 percent of the detector’s worldwide sales, with privately held Louroe making up the other 10 percent. He said the Axis cameras, which can cost tens of thousands of dollars including back-end systems, contain more recent, sophisticated versions of the software than the Louroe equipment does.The Louroe spokesman said its devices receive regular software updates. Axis did not respond to ProPublica’s requests for comment.Van der Vorst acknowledged that the detector is imperfect and confirmed our finding that it registers rougher tones as aggressive. He said he “guarantees 100 percent” that the system will at times misconstrue innocent behavior. But he’s more concerned about failing to catch indicators of violence, and he said the system gives schools and other facilities a much-needed early warning system. It “enables them to act much faster when there’s a potential violent situation,” he said, citing a hospital in Fort Myers, Florida, where the detector alerted security to unruly visitors. An official at the hospital said the software has spotted aggressive behavior before staff could push a panic button, giving security officers a head start on defusing incidents before they escalate.Asked whether his algorithms could prevent a mass shooting, van der Vorst said: “I wouldn’t claim that we could prevent a crazy loony from shooting people.”Sound Intelligence developed its aggression detector within the last two decades. It tested an early model in a Dutch “pub district,” according to a 2007 study co-authored by a company researcher. Microphones were placed in 11 locations in inner-city Groningen, and the detector’s findings were compared with police reports of aggressive behavior. The results were “so impressive,” the study reported, that the device was considered “indispensable” by several Dutch police departments, the Dutch railway company and two prisons.Since then, the software has grown more complex, improving its ability to identify aggressive voices, van der Vorst said. Sound Intelligence engineers said the latest version was calibrated using audio collected in part from European customers, including some recordings of screaming kids. Asked if any of the training data came from schools, van der Vorst didn’t respond directly.Venkatasubramanian said that calibrating an algorithm in one context and then using it in another can build “layers and layers of problems.” He has called for algorithms, particularly those used in public safety situations, to be audited for transparency and bias. Other critics have similarly assailed some policing algorithms that were designed to predict earthquakes but now are used to foresee crime hotspots.
“It’s not clear it’s solving the right problem. And it’s not clear it’s solving it with the right tools.”
Researchers have also found that implementing algorithms in the real world can go astray because of incomplete or biased training data or incorrect framing of the problem. For example, an algorithm used to predict criminal recidivism made errors that disproportionately punished black defendants.Schools and other customers buy microphones preloaded with Sound Intelligence’s software, and then they order a software key from Louroe or another distributor to unlock it. Mounted inconspicuously on the ceiling, Louroe’s smoke-detector-sized microphones measure aggression on a scale from zero to one. Users choose threshold settings. Any time they’re exceeded for long enough, the detector alerts the facility’s security apparatus, either through an existing surveillance system or a text message pinpointing the microphone that picked up the sound. Sound Intelligence and Louroe said they prefer whenever possible to fine-tune sensors at each new customer’s location over a period of days or weeks, although that can’t always be arranged.Pinecrest Academy Horizon, a charter school in Henderson, Nevada, with 720 students in kindergarten through fifth grade, installed two Louroe microphones early this year with both the aggression- and gunshot-detection software packages. One hangs above the reception area and another in a satellite building, part of a repurposed strip mall.Initially, children slamming their locker doors were setting off the gunshot detector. As a result, its sensitivity to noise was adjusted to reduce false positives. Jedidiah Wallace, of Las Vegas-based Atlas Integrated Security, which configured the devices for the academy, said he’s aware of the aggression detector having been triggered once: when a child screamed after being bitten by a classmate.Henderson’s violent crime rate is one-third of nearby Las Vegas’ and less than half the national average, according to 2017 FBI figures. Still, “we needed a bit of extra peace of mind,” said Pinecrest Principal Wendy Shirey, who wears a panic button around her neck that can alert local police.Rock Hill Schools in South Carolina, across the state line from Charlotte, installed the Sound Intelligence software on Axis cameras last year. Audio feeds from one of the district high school’s surveillance cameras alert security officers to aggressive sounds indicating a possible scuffle in the cafeteria or common area.On one occasion, students who loudly wished their friends a happy birthday triggered the detector, said Rock Hill’s security director, Kevin Wren. Nevertheless, he said: “It has worked on picking up aggression. My thought is: Maybe I can reduce the response time of students getting into a fight. The next punch could break their nose.” Van der Vorst said the detector has helped to reduce aggressive incidents at the school.The software has been less effective at The Valley Hospital in Ridgewood, New Jersey. Daniel Coss, security chief for the hospital’s health system, said he’s phasing out the detector after a three-year, $22,000 pilot program. The devices—placed in public, “high risk” areas—had been set off by patients’ loud voices and cafeteria workers slamming cash registers closed. Once the detector was tweaked to be less sensitive, it ignored an agitated man who was screaming and pounding on a desk. The situation escalated until six security officers responded.“He was doing everything that should have set off the system. And it didn’t,” said Coss, who believes the technology could work in another setting.
Van der Vorst said he feels “terrible” about the detector’s failure to alert the hospital. “I will definitely take action on this. They shouldn’t have that experience.”ProPublica purchased a Louroe microphone and set it up in line with guidance provided by Sound Intelligence. Reporters then observed the aggression detector’s response to noises made by high school seniors as they played games in the library (at Sinatra) or a common room (at Staples), and in small adjoining rooms in both schools where they screamed on cue and read aloud comic strips in which characters vented frustration, fear and anger. Of 55 instances in which the Sinatra students screamed, 22 set off the detector.Van der Vorst questioned some of ProPublica’s findings, like the missed screams , because of a phenomenon known as "clipping." That’s when a microphone becomes overwhelmed by too much noise, distorting the sound and potentially throwing off the algorithm's readings. Clipping can happen when loud sounds are recorded in a small room, so ProPublica retested the students in a larger space using the same prompts. Many screams , including Russcol’s, again failed to trigger an alarm—indicating that clipping had not made a significant difference in our results.During our first round of testing, when pizzas were delivered for lunch in the Sinatra library, the cheering triggered the detector. So did each round of Pictionary as students shouted guesses—“A fireman !” “Lucifer!”—until the artist revealed the correct answer (Burning Man, the festival in remote Nevada). Laughter sometimes set it off, especially raucous guffaws that the detector apparently mistook for belligerent shouts.
In response to mass shootings, some schools and hospitals are installing microphones equipped with algorithms. The devices purport to identify stress and anger before violence erupts. Our testing found them less than reliable.
How We Tested an Aggression DetectorTo test the algorithm, ProPublica purchased a microphone from Louroe Electronics and licensed the aggression detection software. We rewired the device so we could measure its output while testing pre-recorded audio clips. We then recorded high school students and analyzed the types of sounds that the algorithm said were aggressive.
We found that higher-pitched, rough and strained vocalizations tended to trigger the algorithm. For example, it frequently triggered for sounds like laughing, coughing, cheering and loud discussions. While female high school students tended to trigger false positives when singing, laughing and speaking, their high-pitched shrieking often failed to do so.
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