The Toronto Police have purchased four sonic cannons for the G20 summit, but 'promise' they will be mostly used as a “communications tool.”

The Long-Range Acoustic Devices (LRADs) can be used for sending “directions for evacuation” or “prerecorded messages,” said Toronto Police spokeswoman Meaghan Gray in an interview last week. “The devices will be used as a communications tool.”

But, she added, the LRAD “does have an alert function and if necessary to use that, we will.”

In terms of security weapons, LRADs are anathema to anti-capitalist protesters, dispensing prerecorded messages about “unlawful assembly” before dispersing crowds with targeted blasts of sonic fury. The decibel level approaches that of a bystander on a tarmac listening to a jet taking off.

Makers of the LRAD boast their technology can quickly disperse any mob without hurting anyone. The devices are produced by California-based LRAD Corp.