CONTROL SONORO

Perhaps not, but it can certainly stop people in their tracks. On Saturday a group of pirates off the cost of Somalia discovered just how powerful sound can be, when their attack on a luxury cruise liner was thwarted by an ear-splitting blast. The captain of the Seabourn Spirit used a “sonic blaster” to ward off the raiders as the ship rounded the Horn of Africa. Armed pirates don’t usually get put off by a bit of noise, but the sonic blaster is a bit more sophisticated than bagpipes or ram’s horns.

The latest in naval noise weaponry was developed by the American military after the 2000 attack on the USS Cole, off Yemen. That prompted the invention of the “long range acoustic device” (LRAD), designed to keep small boats away from warships. The US military has been using it since 2003, and now some cruise ships have been fitted with it, to protect their wealthy passengers.

“LRAD is much more efficient than the usual loudspeaker,” says Dr Jurgen Altmann, an acoustics expert from the University of Bochum in Germany. “The secret comes from combining lots of small loudspeakers on to a big surface. This large sound source enables the beam to be more focused and transmit its message over a distance of up to 500 metres.”

“It is like an advanced form of loudhailer, which specifically directs the sound rather than bathing everyone,” says Neil Davison of the Non-Lethal Weapons Project at the University of Bradford.

LRAD is probably what the captain of Seabourn Spirit used against the pirates, but why should a hi-tech speaker system scare them? “If they were naive pirates and they suddenly heard an announcement, seemingly from very nearby, then they may have become confused,” says Altmann. Alternatively, if the pirates were close to the ship the noise may have simply hurt their ears – when set to its warning mode it registers up to 150 decibels. “Over short distances the sound is well above the pain threshold for hearing and could cause permanent damage,” says Davison.

Pirates are not the only people to be deterred by noises from a LRAD. Insurgents in Iraq and looters in New Orleans have been vanquished by an LRAD howl. And it might just be the start of a new wave of noisy instruments designed to give authorities the upper hand. One instrument in the pipeline is a special wand-shaped speaker that could be used in aircraft against hijackers. “It is a tube, about a metre long that emits a directed, high-frequency sound, which hurts unprotected ears,” says Altmann.

Sonic weaponry is even rumoured to have its place in the entertainment world. In 2002 Gaspar Noe’s film Irreversible was claimed to feature low frequency sounds during its first 20 minutes to create disorientation and unease among the audience. And in the mid-1980s the US band Swans told journalists they deliberately played at volumes designed to make fans at their shows vomit.

Scientists dispute the veracity of these claims, suggesting that you would be more likely to be disturbed by low-frequency sounds if you went to see a science fiction movie about them. One day, however, it may be possible to disable your enemy by playing a sound that makes them feel sick.