Canadian police Friday won a green light to use ear-splitting sonic cannons if needed to control protests planned against a G20 summit in Toronto this weekend, but only on their lowest setting. A Canadian court threw out a case brought by the Canadian Civil Liberties Association (CCLA) which had sought an injunction against the use of such canons, fearing they could become powerful weapons against protestors. Canadian police purchased four of the Long Range Acoustic Devices, also known as sound cannons, for crowd control at the G8 and G20 summits. The devices can emit ear-splitting pitches up to 150 decibels that can affect people from more than 200 meters (650 feet) away. They can be heard several kilometers (miles) away. Police insisted they would not be used as weapons, but merely as 'communication tools' with protesters. Civil rights activists however argued that the canons, 'originally developed for use on the high seas, and subsequently used in war zones in Iraq and Afghanistan,' were 'dangerous' and not appropriate for urban policing. Ontario Superior Court judge David Brown ordered police to 'refrain from using the Alert function on their units.' On this setting, the devices emit 'a high decibel, narrow frequency, focused set of sound waves' that can seriously damage a person's inner ear. He called on police to 'adopt the distance and volume limitations' for the devices -- in other words not to walk up to a person and blast them. But Ken Georgetti, president of the Canadian Labor Congress, lamented the presence of the canons, saying it could scare away protestors who have a legitimate right to express their views. 'Several individuals have expressed their concerns about suffering permanent hearing loss from the sound cannons to me,' he told the court. 'We are encouraging families to attend, but people are reluctant to bring their children when there is the risk of permanent damage to their children's hearing.' 