In preparation for the thousands of anti-war activists expected to protest outside the NATO summit in Chicago next week, the city has reportedly ordered $1 million worth of riot-control equipment including a 'sound cannon' that can be used to emit pain-inducing sound waves of up to 150 decibels.
According to the Guardian, Chicago police have confirmed that a long-range acoustic device, or LRAD, will be on hand at the protests, and that officers intend to use the device "as a means to ensure a consistent message is delivered to large crowds that can be heard over ambient noise."
"This is simply a risk management tool, as the public will receive clear information regarding public safety messages and any orders provided by police," police spokeswoman Melissa Stratton told the Guardian.
But LRAD devices can also be deployed as "sonic weapons," and U.S. police have used them in that capacity on a number of occasions, Gizmodo reports.
The first documented case of police using the LRAD against activists was at the 2009 G20 summit in Pittsburgh, when police "fired a sound cannon that emitted shrill beeps, causing demonstrators to cover their ears and back up," according to The New York Times.
Pittsburgh police used the device again in 2011 to control crowds outside the Super Bowl, and LRADs have also been reported at various Occupy events.
The U.S. Navy also uses the devices to ward off pirates that attack cruiseliners and other ships, according to the San Diego Union-Tribune.
The LRAD's power lies in its ability to emit sound in narrow 30-degree "beams" as if it were traveling through a "sound tunnel," according to the Union-Tribune. Set at 150 decibels, the sounds can reach a target as much as 1,600 feet away.
But the human threshold for pain is between 110 and 120 decibels -- about the level of a jet taking off -- so using the device at its maximum power could cause irreversible damage to the ears, according to the Toronto Star.
In fact, according to the U.S. National Institute on Deafness, noise above 85 decibels can cause permanent hearing damage.
Karen Piper, a former visiting professor at Carnegie Mellon University who attended the G20 summit in Pittsburgh, sued the city after allegedly sustaining permanent hearing loss when the city used their LRAD.
"The intensity of being hit at close range by a high-pitched sound blast designed to deter pirate boats and terrorists at least a quarter mile away is indescribable. The sound vibrates through you and causes pain throughout your body, not only in the ears. I thought I might die," Piper, now an English professor at the University of Missouri, said in a press release. "It is shocking that the LRAD device is being promoted for use on American citizens and the general public."
But LRADs appear to be here to stay, at least for now. Last week, Britain's Ministry of Defense announced that they will deploy a sound cannon during the 2012 Summer Olympics in London, where it will mostly be used to blast verbal warnings to boats on the River Thames, according to the Associated Press.
See Chicago police show off their LRAD in an ABC News report, above.