How Do ‘Acoustic Weapons’ Work?

In recent weeks, acoustic weapons like flash bang grenades and sound cannons have come to new prominence in the public consciousness thanks to their inclusion in the arsenal of weapons used by U.S. police against protesters.

Flashbang grenades, also called stun grenades, are explosive devices that emit an extremely loud bang and bright lights when detonated, and are intended to disorient people. A long range acoustic device (LRAD), also called a “sound cannon,” is a speaker system and sound energy weapon is used to disperse crowds by emitting an extremely loud, high frequency noise that can cause pain, disorientation and injury to those exposed. In a particularly prominent recent example of their use,  MSNBC reporter Jo Ling Kent was hit by a flashbang grenade while on live TV, reporting on the protests in Seattle.

And although both types of devices are intended only to disorient people, flashbang grenades and sound cannons can cause very serious injuries.

Flashbang grenades

One potential injury from a flash bang grenade is hearing loss. Their detonation causes a noise that is louder than a jet engine and can cause temporary deafness, ear ringing and loss of balance. If a person is near enough to the flashbang grenade when it detonates, the hearing loss may be permanent. Other injuries can result, whether from the force of the explosion or the heat generated by the detonation itself—when the flash powder ignites, it does so with temperatures hotter than lava.

The use of flashbang grenades by police is poorly documented. A 2015 ProPublica investigation found at least 50 Americans, including police officers, had been seriously injured or killed by flashbang grenades since 2000. Many more casualties may have gone unreported, as few records are kept on the number of times police have used them.

Perhaps the most notable injury was to a 19-month old baby boy who was seriously injured in 2014 during a “no-knock” drug raid in Georgia after officers threw a flashbang grenade into his crib, where it landed on a pillow next to his face, causing burns to his face and throat. Police officers were looking for the family’s cousin, who wasn’t there at the time and who later peacefully surrendered.

The 19-month old was placed in a medically induced coma for a month. He has undergone extensive reconstructive surgeries, and will need more of them as he gets older. The on-going cost of care his care is reported to be $US1.6 million ($2 million), an amount Habersham County, GA initially refused to pay, although the family was later able to settle for $US3.6 million ($5 million) in a civil suit. A grand jury recommended that no criminal charges be brought against the officers.

The use of flashbang grenades is poorly regulated, and training requirements are inconsistent between police departments. If you’re in a position where they are being used against you, there’s not much you can do to safeguard yourself from the worst of their effects. Some sources suggest wearing ear plugs to protect against the noise; others point out that could leave you vulnerable if the earplugs reduced your hearing during a rapidly changing situation. The most you can do is to try and avoid getting hit in the first place—which, given the apparent predilection for police use of retaliatory acts against peaceful protesters, is easier said than done.

Sound cannons

A sound cannon looks like a big, bulky stereo system, and is capable of releasing sounds meant to disorient. Injuries from the use of sound cannons can include a persistent ringing in the ears that can last for minutes or days, headaches, nausea, sweating, vertigo and loss of balance. More serious effects can include permanent hearing loss.

A sound cannon was used against people protesting the death of Eric Garner, and six people in close proximity to the device developing symptoms afterwards including migraines, sinus pain, dizziness, facial pressure and ringing in their ears. During more recent protests, sound cannons have been used against protesters in Portland, OR; San Jose, CA; Colorado Springs, CO; Phoenix, AZ; Columbus, OH; Charleston, SC; and Ft. Lauderdale, FL; among other cities.

To avoid avoid injury if you note that police have set up a sound cannon, your best bet is to watch for signs it is about to be put into use. An indicator might be if they use the sound cannon as a loudspeaker first, and tell protesters to clear the area.

If you think police are about to use a sound cannon, the farther away you can get from it, the better. It can also help to find shelter against a hard surface, such as brick or cement, that can deflect sound waves. Another strategy is to put in earplugs or earmuffs, as long as you are in a safe position to do so—keeping in mind that in large crowds, situational awareness is paramount. Regular earplugs or cotton balls won’t work, nor will your average noise-cancelling headphones. Instead, you would need safety earmuffs or earplugs, such as the kind used to protect your hearing at a shooting range.