Long Range Acoustical Device

Nov 16, 2007 15:27 GMT  ·  By

For years the usual tactics used by the U.S. army or Special Forces involved weapons designed to inflict high damage or to kill the enemy. The reason for this was not the will to kill someone, but rather because there was no alternative to stop a person. If you wanted to stop a group of armed to the teeth people, there was nothing that you could do, except to use firearms.

As time passed and technology evolved, people started to change their mentality and found alternative devices to the fire arms. Now a multitude of non-lethal weapons exist, such as taser guns, laser dazzlers, pepper sprays and sonic blasters. Their main goal is to inflict enough pain to stop a person, without killing them, or creating extensive or permanent tissue damage.

Urbanization in crisis-prone regions creates potential large vulnerable groups of civilians to be trapped in volatile operations, in urban terrain, so techniques and tools that are not lethal are essential in these areas.

Such an example of non-lethal weapons is the LRAD or the Long Range Acoustic Device, which is a sonic blaster device, which concentrates a wave sound on a person at incredible high volumes. But unlike other sonic devices, the LRAD doesn't spread sound all around the central sound emitter, but it directs it in a single direction.

Sound, unlike light, needs a medium through which to travel. That is the reason why you can't hear sound in void. No matter what it creates it, sound always travels in wave. Sound is made by creating a disturbance in the matter, such as a vibration. Vibration from the source material is transmitted by the surrounding matter through waves.

Different sound waves can pass through one another without too much distortion, but if there are two identical sound waves, which are out of phase, they cancel one another out; in the same way an elementary particle and its anti-particle cancel themselves out. But using sound wave of the same phase means combining their compression and rarefactions, doubling their amplitude.

One the other hand, LRAD uses high-frequency sound waves, which don't spread as much as the low-frequency wave, meaning that they travel a longer path through the material before they lose their amplitude.

According to the American Technology Corporation, the LRAD has exceptional intelligibility in a 15-30 degree beam and is effective over distances of 1,000 meters. In 2005, LRAD was first used to scare off a group of armed pirates, who wanted to attack the Seabourn Cruise Line, but failed to come aboard the vessel due to the extreme sounds with which they were blasted. The U.S. Army has reported that the same device was used in the war in Iraq, to force insurgents to come out of certain buildings and hiding places.

The human threshold of pain for loud or high-frequency sounds, is about 130 dB, the LRAD being able to provide a volume of 146 dB in continual mode, or 151 dB in bursts or sound.