Protest groups have been warned sonic cannons could be used against them should their G20 demonstrations get out of hand.

But while it acknowledged it had such devices in its arsenal, the Queensland Police Service has insisted the "long range acoustic hailing devices" would not be used as a crowd control measure.

Sonic tool: A long-range acoustic device at the G20 summit in Pittsburgh. Credit:YouTube

Fairfax Media understands the Queensland Police Service has in its possession at least two models – the LRAD 500X-RE, which has a range of two kilometres, and the handheld LRAD 100X, with a range of more than 600 metres.

One of the groups informed of the potential use of the devices, the Brisbane Community Action Network, was offered the opportunity to see a demonstration of the LRAD sonic cannons in action