'Sonic weapon' to be deployed during London Olympics

The spokesman said: "As part of the military contribution to the police led security effort to ensure a safe and secure games, a broad range of assets and equipment is being used by our armed forces.

"This includes the LRAD (Long Range Acoustic Device) which will be deployed during the Olympic Games primarily to be used in the loud hailer mode as part of the measures to achieve a maritime stop on the Thames."

The piercing beam of sound emitted by the device is highly directional. Some versions of the LRAD are capable of producing deafening sound levels of 150 decibels at one metre, the 'BBC' reported.

But the device can also be used to broadcast verbal warnings, such as ordering crowds to disperse.

The San Diego-based LRAD Corporation has previously sold the device to the US Army, which deployed them in Iraq for crowd control. They have also been bought by the US Navy and Air Force.