A student who went to photograph a Black Lives Matter protest was warned that New York City police might use a sound cannon against demonstrators.
"My friend said, 'If you hear this, plug your ears and run,'" Anika Edrei recalled.
So, when the NYPD fired a LRAD, or Long Range Acoustic Device, at the demonstration in 2014 in Manhattan, that's exactly what Edrei, 24, did.
Now New York officers' use of the sound cannon at that protest is the subject of what may be the first lawsuit in the nation over police deployment of such devices, the plaintiffs' lawyer, Gideon Oliver, says. After a couple of years of the case winding its way through the courts, the U.S. Supreme Court declined to hear the NYPD's motion for dismissal, allowing the suit by Edrei and five other plaintiffs to proceed.
After police used the device at the demonstration, which was over a grand jury's decision not to indict NYPD officer Daniel Pantaleo in the killing of Eric Garner, "I experienced a pretty strong migraine and dizziness almost immediately," Edrei told NBC News in an interview.
"I remember sitting down on the side of the street after I had gotten away and feeling very confused," said Edrei, then a photojournalism student at the International Center of Photography in New York City.
The migraine lasted about a week, but almost five years later, Edrei, now a student in Edinburgh, still feels the LRAD's effect.
Having never had hearing issues before that day in 2014, the sound of sirens in the U.K. now causes Edrei immediate pain.
Another plaintiff was told by his doctor that the pressure of the noise pushed a bone in his ear inward, damaging a nerve, according to court documents. Some also said they are now afraid to attend protests, which harmed their journalism careers.
Created for the U.S. military after the terrorist attack on the USS Cole in 2000, LRADs were designed as acoustic weapons meant to repel anyone exposed to them. By emitting sound at an almost-intolerable amplitude, they force people in the device's path to flee. Police departments started purchasing non-military LRADs in the early 2000s, they say as a way to control crowds and protests without having to use other more forceful means.
But in the federal civil rights lawsuit, the plaintiffs claim officers' use of the LRAD at the protest was excessive force, violating their constitutional rights.
The suit against the NYPD and individual officers seeks damages and for the police to refrain from using LRADs on civilians until more studies, guidelines, and trainings are in place.
The officers have argued that because LRADs employ sound, they are not an "instrument of force." The defendants have also claimed they should be afforded immunity because the officers were unaware the use of LRADs could violate protesters' constitutional rights.
In a statement to NBC News, the NYPD said that at the 2014 protest, "two officers used an LRAD to direct unruly protesters at a volatile public demonstration." The officers "acted appropriately," the statement said, calling the LRAD "a safe and effective communication tool that provides an alternative to use of force or making additional arrests."
The lawsuit case has no legal merit, the NYPD added. "Exposing police officers to civil liability for using tools that successfully substitute for the use of force is bad for both public safety and police community relations," the statement said.
Adam Scott Wandt, an assistant professor of public policy at John Jay College of Criminal Justice, said the LRAD can be a weapon in addition to a communication tool.
An LRAD, which looks like a large black speaker, can function as a public-address system, giving police a way to communicate with a large crowd, Wandt said. Activate what is called the "area-denial function" on the device and it becomes a "sonic weapon," he said.
On the model purchased by the NYPD, the control panel warns in all capital letters, "Do not enter within 10 meters during continuous operation" when the LRAD is employing the area-denial function, court documents said.
"Making someone feel pain and discomfort is a use of force," Wandt said.
LRAD Corp., which makes the device, did not respond to NBC News' repeated requests for comment.
"The officers that used this technology knew or should have known it would cause pain in the protesters that they are using it on," Wandt said, "The government has very well documented... that damage could occur with sounds over 100-120 decibels. This product clearly exceeds those limits."
In the case of a violent protest, Wandt said he understands why police might want to use LRADs in place of potentially lethal force.
But, he said, "When law enforcement adopts new technologies, they have a responsibility to understand how they work, especially before they use them on a civilian population that is nonviolent," like at the protest Edrei attended in 2014.
Edrei hopes the suit will lead to others being protected from the sonic device's harmful effects and lead to policy change.
"I'm concerned about how indiscriminate the LRAD is," Edrei said. "Anyone who is in earshot of the machine is going to experience it, and that really scares me."