Protesters marching at the G20 summit next month may be greeted with ear-splitting sound cannons," the latest Toronto police tool for quelling unruly crowds. Toronto police have purchased four long-range acoustic devices (LRAD) - often referred to as sound guns or sound cannons - for the upcoming June 26-27 summit. Purchased this month, the LRADs will become a permanent fixture in Toronto law enforcement, said police spokesperson Const. Wendy Drummond. "They were purchased as part of the G20 budget process," Drummond said. "It's definitely going to be beneficial for us, not only in the G20 but in any future large gatherings." But critics say they are really non-lethal weapons and infringe upon protester rights. LRADs can emit ear-blasting sounds so high in frequency they transcend normal thresholds of pain. LRADs are being increasingly employed as a crowd-control device and at last year's G20 summit in Pittsburgh, police used them on protesters before deploying tear gas and stun grenades. The acoustical devices can also be pointed at specific targets, transmitting a "laser" of sound that is less aggravating for anyone standing outside its beam.