The so-called sound cannons purchased by Toronto Police for the G20 summit will be the focus of a court hearing Wednesday.

Lawyers representing the Canadian Civil Liberties Association and the Canadian Labour Congress will be at the University courthouse Wednesday morning seeking a court injunction. The groups are hoping a judge will stop police from using long-range acoustic devices, or L-RADs, on protesters.

The devices emit ear-piercing blasts that can cause permanent hearing damage, the groups say. Toronto Police purchased four L-RADs last month and insist they will be used as communication tools that will broadcast pre-recorded messages and not as weapons against protesters.

A judge is expected to release a decision on the L-RADs by Friday morning. The CCLA and CLC are hoping for a decision by Wednesday afternoon.

The potential use of sound cannons to control crowds during the G20 summit has been a controversial issue. Authorities in Pittsburgh came under fire for using them against demonstrators during the G20 summit in that city in September 2009, which was the first time L-RADs had been used in public.

Officers on the streets in Toronto will be using three 100x model L-RADs (see specifications here) that are worn on the body and a larger 300x model (specifications here) could be used by the marine unit, if needed.