This story includes audio designed to be listened to with headphones. The sounds are recordings of actual gunfire and fireworks.
Chicago residents who wonder whether they’re hearing gunshots or fireworks around Independence Day may be interested to know that even technology sometimes struggles to distinguish between the two.
“July 4th is a challenging period for us,” said Ralph Clark, CEO of ShotSpotter, a company that provides the Chicago Police Department with acoustic surveillance systems designed to detect gunshots.
Shotspotter will have additional staff working around the holiday to help analyze loud sounds to determine if they are gunshots, Clark said. In Chicago, police use the information from ShotSpotter in four high-crime districts, and officers can get alerts on the time and location of gunfire on their department-issued cell phones, said Chief Jonathan Lewin, who oversees technology for CPD.
“If [ShotSpotter staff] are not exactly 100 percent sure, we tend to err in the direction of pushing an alert out,” Clark said. “We don’t like false positives, we don’t like false negatives, but if we had to choose our poison, I think we would probably choose more of the false positive.”
WBEZ recorded the sound of gunfire and the sound of fireworks to hear if they sound different.
William Zeller, a firearms instructor in Northwest Indiana, said he has been shooting guns since he was 21 years old. He said he can easily tell the difference between the sounds that different guns make and the type of bullets fired. For example, he can tell whether a 9mm bullet or a .45 caliber bullet was fired based on the amount of noise from the gunshot. Still, he said he can’t always tell fireworks from pistol fire.
“It depends on the sound environment, the geography,” Zeller said. “Usually fireworks have a lighter tone — almost tinny tone. And with no projectile, there’s not going to be any sound wave from the bullet travelling. But it can be difficult in certain circumstances.”
Listen to Zeller describe the guns he is shooting here:
Shelton Fireworks in Porter, Indiana sees plenty of Chicagoans in the days leading up to Independence Day, said store manager Gary Shelton.
Even a fireworks expert like Shelton can have trouble telling the difference between a gunshot and a firework.
“It is hard to know in the city, isn’t it?” Shelton said. “If you’re going to have something that has a good crack and a bang to it — that’s going to kind of mimic some kind of gunshot — it’ll be a fairly big firework piece. Hopefully the firecrackers that make those kinds of louder sounds are hard to come by and not too common.”
Listen to Shelton describe two popular items that sell for the holiday and what they sound like:
An earlier version of this story misidentified the title of police Chief Jonathan Lewin. He is chief of the police department's Bureau of Technical Services and not a deputy chief.
WBEZ producers Gabrielle Wright and Miles Bryan contributed to this story.