A device that can be used as a sonic weapon will be deployed in London for the Olympics.
The American-built long-range acoustic device (LRad) can be used both as a high-powered loud speaker and to emit an ear-piercing beam of sound.
The Ministry of Defence confirmed that it was among a "broad range of assets" being used by the Armed Forces to provide security during the Games.
A spokesman said it would be used primarily in "loud hailer mode" in order to issue verbal warnings to any boats on the River Thames that were causing concern.
However, the LRad can emit a highly focused beam of sound at a pain-inducing 150 decibels (dB).
In comparison, military jets have a take-off rating of 140 dB while instant perforation of an eardrum can occur at 160 dB.
The US army deployed LRad as a crowd control device during its struggles in post-war Iraq.
More recently, it used a vehicle-mounted system against G20 protesters in Pittsburgh in 2009 , driving back US demonstrators with the LRad's high-pitched sound.
The devices have also been used on cruise liners to ward off Indian Ocean pirate attacks.
Some models are now "man portable" backpacks that can blast alarm warnings at 137 dB, and can be used as land-based loud hailers with a range of 1km.
"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," the MoD spokesman said.
"This includes the LRad 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."