Police in Pittsburgh are using sound blasters and other non-lethal weaponry to ward off protesters at the G-20 summit. The sonic weapon is the LRAD or Long Range Acoustic Device, a super loud-hailer deployed by U.S. forces and famously used to fight off pirates.

According to the Guardian, LRAD is being used in two ways: as a megaphone to order protesters to disperse, and, when they disobey, as an “ear-splitting siren” to drive them away. This has happened repeatedly, with the crowd assembling again a few streets away. It’s one of a number of controversial tactics being employed in the city; check out this video of a seeming “snatch-and-grab” arrest in the middle of a demonstration.