A Sound Weapon to Use in an Emergency
The events of 11th September have focused attention on the question of safety in aeroplanes. In-flight armed guards might be able to prevent hijackers taking over, but what could they be armed with? Researchers in America have come up with a solution that would immobilize attackers but cause no damage to the plane: a sound gun which literally fires out a bullet of sound to inflict pain and disorientation. The man who invented this device, Elwood Norris, tried it out on himself. "It almost knocked me off my butt" he said. "You could virtually knock a cow on its back with this". This is not surprising as the gun gives a pulse of sound at over 140 decibels, and sound becomes painful between 120 and 130 decibels. The sound gun causes intense pain to the eardrum, and hearing loss for a few hours. But it also disorientates people by shocking the inner ear, which affects their balance. The gun works in the same way as hi-fi speakers, by producing pressure waves. However, in the gun these are magnified many times over. This might all sound too good to be true (excuse the pun). However, there are some drawbacks. The sound wave can't be directed at just one person, and the hearing loss it inflicts could be permanent.