Audio producer Cory Choy was reporting on the 2014 Black Lives Matter protests in New York City when he first experienced sound as a weapon.
“Horrible, nauseating pain hit my body,” he tells Popular Mechanics, “and then I realized it was sound. At first you just think, ‘What’s happening to me?’ Your body goes into complete pain and panic mode. It’s the sound equivalent of looking into the sun.”
Despite his professional-grade headphones, the effect of the weapon—a long-range acoustic device, or LRAD—was so disorienting at first that Choy couldn’t tell which way to run and was forced to randomly pick a direction. But he was lucky.
“People in the direct line of fire [of the LRAD] didn’t run,” he says. “They just dropped to the ground and started screaming.”
Confronted with an unprecedented global movement against police violence and racial injustice, U.S. law enforcement officers have once again resorted to sonic warfare. What appears to be a projector, a box amplifier, or a loudspeaker mounted on a police car or strapped to an officer’s chest is a relatively modern military-grade deterrent that creates powerful sound waves to disorient and injure humans in its narrow target beam.
These devices vary in appearance and size, but every model has the same two capabilities. In one mode, the LRAD acts as an amplifier, projecting a human voice or recording across thousands of meters; in the other, it emits a “deterrent tone” so loud it can cause permanent hearing loss.
The Early Stages of Sonic Warfare
The first LRADs were developed as military weapons in response to the bombing of the USS Cole off the coast of Yemen in 2000. Military officials asked the LRAD Corporation (now Genasys) for a device with two functions: to communicate at a distance with potential threats, and to disperse them with an unbearable alarm-like sound.
These military-grade weapons soon found their way ashore and into the hands of police. Protesters have reported LRAD attacks by police at the NODAPL protests at Standing Rock, during the 2017 Women’s March in Washington, D.C., and in dozens of other cities and demonstrations around the world.
Over the past few weeks, as worldwide protests have erupted in response to the May 25 murder of George Floyd by Minneapolis police officer Derek Chauvin, reports of police using LRADs against civilians have again poured into social media feeds. And with the renewed use of LRADs comes a renewed concern for their danger.
“Humans are regularly exposed to noise that can cause damage over time, but LRADs can cause lasting hearing damage in a matter of seconds,” Marisa Ewing-Moody, a Black audio engineer who has been educating the public about the danger of LRADs on Twitter, tells Popular Mechanics.
Any sounds above 85 decibels (dB) can cause permanent damage to your hearing depending on how long you’re exposed to them, Ewing-Moody says.
“Normal conversation is about 60 to 70 dB, concerts and sporting events can be about 94 to 110 dB, and a jet taking off can be between 120 and 140 dB,” she says. “In contrast, some LRADs can create sounds up to about 160 dB when used at their full power.”
A Car Alarm From Hell
The purpose of LRAD systems, according to the Genasys website, is to provide “unparalleled long-range communication and safe, scalable non-kinetic escalation of force.” But sound technicians and human rights defenders around the world have disputed this framing, comparing sonic weapons to other controversial “dispersal” tactics like tear gas and rubber bullets.
Robert Auld, an audio engineer and former chair of the New York chapter of the Audio Engineers Society, is one of many in his trade who sees LRAD deployment as a military-style escalation of force.
“I would characterize it as a terror weapon, up there with tear gas and flash-bang grenades,” Auld tells Popular Mechanics. “The latter are supposed to be ‘non-lethal,’ but they can hurt you. Same for the LRAD.”
The principle behind using an LRAD as crowd control, rather than for long-distance communication, is similar to the idea behind a whistle or a siren: they all emit tones in the most sensitive range of frequencies for most humans. At a distance, an LRAD deterrent tone may sound like any other alarm.
But while whistles emit sound waves in all directions, LRADs concentrate the waves in a narrow cone of sound, extending about 15 degrees in every direction from the axis, like a flashlight. This “directional” sound wave packs the typically diffuse kinetic energy into a tight space, bombarding those in its vicinity with a powerful tone that’s an annoyance at a distance … and a serious medical threat up close.
The Cone of Pain
There are a few competing theories about the exact mechanisms that give the LRAD its power, due in part to the scarcity of technical information about the devices online. Some articles suggest the drivers inside the device use piezoelectric transducers, which convert electrical impulses to high-speed vibrations, emit sound waves in the ultrasonic range.
But Auld suspects it’s more low-tech than that. In his estimation, the LRAD uses a pair of ordinary off-the-shelf drivers, much like the ones that power old-fashioned bullhorns, mounted in a frame that encloses and redirects the sound waves until they all head in the same direction.
This limited frequency range—200 Hz to 10 kHz, roughly the same as human speech—combines with the efficient drivers and horn loading to produce the destructive tone.
“It is a brute force design dedicated to a single purpose: playing really loud in the most sensitive part of human hearing,” Auld says. “There is nothing particularly sophisticated about it.”
Protect Your Ears and Get Out of the Way
As reports of LRADs used on civilians roll in, sound specialists and DIYers have scrambled—unsuccessfully—to find some way to mitigate the weapons’ effects. Cheap foam ear plugs provide some protection, up to 30 dB, while covering your hands with your ears reduces noise by around 20 dB. But the best protection is to get out of the direct beam of the weapon.
“Remember that the LRAD beams sound in a narrow pattern, so move off to one side to get out of the main pattern,” Auld says.
In a widely circulated 2017 digital zine on sonic care for protesters, audio engineer Daphne Carr laid out practical insights for responding to LRADs while in the streets. “If it is used as a communications device, put in ear plugs and check out the scene for routes of escape from possible injurious exposure,” she wrote.
Carr suggested treating LRADs as a warning from police that they’re about to escalate violence, even if it starts out as a public service announcement. LRADs are frequently used in conjunction with other suppression tactics like targeted arrests and pepper spray; one form of escalation should alert protesters to defend against additional forms.
In general, Carr wrote, “police departments are supposed to issue warnings prior to escalations and arrest. This often happens through the LRAD. If you hear a warning from the police, it is likely that this signals that they are planning escalated next steps, be it seizure or use of deterrence tone.”
Is This Thing Legal?
In 2017, a group of New Yorkers sued the NYPD for damages resulting from sonic attacks during the protests that followed the non-indictment of Daniel Pantaleo, one of the officers who murdered Eric Garner in 2014. The department argued loud sounds can’t constitute a use of force, which the judge rejected, allowing the case to proceed. An earlier suit in Pittsburgh awarded $72,000 to a bystander who suffered permanent hearing loss from an LRAD attack in 2009.
“This is why LRADs should be banned against civilians, especially those exercising their right to peacefully protest,” Ewing-Moody says.
While LRADs can cause migraines, dizziness, and hearing loss in the short term, people exposed to them can experience those same symptoms when they hear lesser loud noises, like sirens, says Ewing-Moody.
“People should be able to protest safely,” she says, “without fear that sonic weapons designed for war will be used against them.”
Lynne Peskoe-Yang is a science writer and researcher in New York. Her reporting on civil engineering, machine learning, and artificial intelligence has appeared in Marketplace, IEEE Spectrum, Rewire.org, and Sludge; her essays on science and language live over at Popula.
