Olympics-Rights group worried about Vancouver "sonic gun"

* LRAD can fire concentrated blast of sound

* Group fears may be used against protests at 2010 Games

* Police say LRAD to be used only as public address system

By Allan Dowd

VANCOUVER, British Columbia, Nov 10 (Reuters) - A Canadian civil liberties group accused police on Tuesday of quietly buying a high-tech audio weapon for possible use against protesters at next year's Winter Olympics in Vancouver.

The so-called long range acoustical device (LRAD) can fire a concentrated blast of sound powerful enough to cause hearing damage and temporary vision disruption, according to the British Columbia Civil Liberties Association.

The group, monitoring security for the 2010 Games, said there should have been independent safety testing of the "sonic gun" before Vancouver Police were allowed to buy it, executive director David Eby said.

The purchase, which was never publicly announced, "reduces the credibility of blandishments from city officials about not interfering with lawful and peaceful demonstrations," the civil liberties group said.

Vancouver Police bought the device last summer to communicate with large crowds and during natural disasters where audio systems such as hand-held megaphones are not effective, according to spokesman Constable Lindsey Houghton.