Police ordered protesters to disperse at the Group of 20 summit last week with a device that can beam earsplitting alarm tones and verbal instructions that the manufacturer likens to a "spotlight of sound," but that legal groups called potentially dangerous.
The device, called a Long Range Acoustic Device, concentrates voice commands and a car alarm-like sound in a 30- or 60-degree cone that can be heard nearly two miles away.
It is about two feet square and mounted on a swivel such that one person can point it where it's needed. The volume measures 140-150 decibels 3 feet (1 meter) away, louder than a jet engine, but dissipates with distance.
Robert Putnam, spokesman for the manufacturer, San Diego-based American Technology Corp, said it's "like a big spotlight of sound that you can shine on people."
"It's not a sonic cannon. It's not the death ray or anything like that," Putnam said.
"It's about long-range communications being heard intelligibly."
During the Pittsburgh protests, police used the device to order demonstrators to disperse and to play a high-pitched "deterrent tone" designed to drive people away. It was the first time the device was used in a riot-control situation on US soil, according to American Technology and police.