MONTREAL -- Anarchists, rioting hockey fans and students beware: Montreal police have two new weapons in the war on public disorder.

Montreal police have purchased two LRAD sound cannons, similar to ones used by Toronto Police during the G20 summit. The cannons, the LRAD 100X and the LRAD 300X, cost $6,000 and $12,000 respectively.

They can generate up to 140 ear-splitting decibels to disperse pesky crowds, but the cops promise not to pump up the volume unless people get really unruly.

"I don't see this as a weapon," said Inspector Roch Deroy of the Montreal police. "It's more as a means of delivering a clear message to a crowd, or in a hostage situation. It delivers messages through walls."

A city report made several recommendations on how best to use the cannons safely. Among the suggestions are to not sound alarms continuously and to never use the cannon if people are within 10 metres of the device.