What if there was a weapon whose effects you couldn't see or hear,
but could kill you from a distance of hundreds of metres?

Fergus Day assesses the disturbing potential of infrasound.

Picture the scenario. You're walking through a busy city street when a disturbance breaks out. Suddenly, you're engulfed by a mass of heaving bodies. You struggle to escape, but find your way blocked at every turn. Amid the chaos, you hear the sound of approaching police sirens. When the officers arrive, however, they are not carrying the usual riot shields and batons; they have only what look like large speakers, held out at arms length Suddenly, you feel as if you cannot breathe; your head is pounding as you stumble to your knees. Overcome by nausea, you try to get up, but are engulfed by a feeling of intense anxiety and cannot move. As you lie there, vomiting uncontrollably, those around you are dropping like flies. In the end, the entire crowd is writhing in agony as the police wade in to make arrests. In the aftermath of your ordeal, you recover completely, but one question remains: what caused the devastating physical effects you experienced? You were not hit by a rubber bullet, you saw no tear gas or other noxious substance in the air. So why did so many people fall to the floor as if overtaken by some crippling disease? The answer is simple. You and those around you had fallen victim to a new and terrifying weapon - infrasound.

Sound Logic
For decades, police forces and military authorities throughout the world have been increasingly keen to find methods of containing civil unrest without the risks to their own officers that are associated with current methods of riot control. And, according to a number of researchers, in infrasound, military scientists may now have found the ideal solution to this problem. But what exactly is infrasound and how is it capable of inducing such profound physical effects? Infrasound is a powerful, ultra-low frequency acoustic wave. All the sound that we hear, from the lowest bass to the highest treble, is between 16 and 20,000 Hertz, or cycles per second. Sound waves above or below these levels cannot be heard by the human ear. Because infrasound is, by definition, sound waves of a level below 16 Hertz, it bypasses our ears but can be felt by our bodies in the form of pure vibrations. And it is these vibrations, dependent upon their intensity, that some researchers say can induce a range of symptoms, from nausea, headaches and vomiting, to the rupturing of internal organs and even death. .

Surround Sound
But infrasound is no new invention. In nature, it is produced by powerful and destructive events, such as earthquakes, thunder and erupting volcanoes. The sound waves can travel many kilometres and are not blocked by stone, buildings or other sounds. Infrasound also features strongly in the technology that dominates urban life in towns and cities. Rapidly moving objects such as car engines, fans and air conditioners are responsible for low levels of infrasound that surround us on a daily basis. The fact that certain sound frequencies have definite effects on the human body has long been acknowledged by science. But while ultrasound (frequencies above 20,000 Hertz) has been openly harnessed by science to such mundane ends as repelling vermin or dislodging tartar from dentures, the study and application of infrasound has been far more secretive. Although infrasound research dates back as far as World War I, studies of its effects on human beings did not begin until the early 1960s. At this time, NASA sponsored studies into the potential effects on astronauts of infrasound produced by spacecraft at launchtime. At the Wright-Patterson Air Force Base in Dayton, Ohio, subjects were placed in pressure chambers and subjected to infrasound. Among the resulting effects were 'chest wall vibrations, gag sensations, and respiratory rhythm changes'. Just a few years later, in 1965, the sinister potential of infrasound was fully uncovered. From extensive studies, Vladimir Gavreau, a scientist from the French National Centre for Scientific Research in Marseilles, found that a variety of physical effects were produced when human beings were exposed to ultra-low sound frequencies. He experimented with a series of tubes and organ pipes that produced notes of about 7 Hertz, and found that, by extending the tubes, the sound waves could be directed with some precision. .

Acoustic Lasers
In producing these devices, Gavreau had, in effect, invented 'acoustic lasers'. These narrow beams of infrasound could apparently be aimed accurately, producing nausea, disorientation and headaches in those at whom they were directed. When the infrasound levels were intensified, test subjects also reported feelings of fright, panic and blurred vision. Gavreau believed that a powerful enough infrasound device could knock down walls, break windows and kill everyone within an 8km radius. The device would not be difficult to make, he argued, yet would have a devastating effect. Some researchers have even claimed that, during the late 1960's, the French military became interested in Gavreau's research and used his findings in the development of a growing list of 'secret weapons'. .

Military Appeal
Despite Gavreau's claims, however, many believe that the development of lethal infrasound weapons is highly impractical. Although relatively easy to build, such weapons would have to be extremely large and powerful to kill outright. Nevertheless, research into non-lethal infrasound weapons has continued unabated. The potential of such weapons to break down resistance to interrogation, to induce stress, confusion and disorientation in an enemy has made them particularly appealing to military scientists. If infrasound frequencies could be directed extremely accurately, as reportedly achieved by Gavreau, an individual or a group could suddenly faint, vomit or suffer an epileptic fit, while those nearby would be unaffected. Such devices could also be small and easily carried in an armoured vehicle. .

To many, evidence that such weapons have been under development for decades is provided by a United Nations draft agreement, drawn up in 1976, that prohibited the development of new weapons of mass destruction. Even at that time, infrasound was deemed deserving of special monitoring, owing to the fact that the progress made in the area of acoustics had made infrasonic weapons a viable and attractive possibility. .

Infrasound Tests?
Despite such regulations, many researchers believe that infrasound weapons have already been used on an unsuspecting public. It is claimed, for example, that, during the 1970s, the UK army tested infrasound devices in incidents of rioting and civil unrest in Northern Ireland. And, with ever-increasing levels of investment in non-lethal technology, it would seem that such incidents can only become more common. .

Today, infrasonic devices are among a growing list of 'non-lethal' weapons - including stun guns, electromagnetic mind-control devices, and chemical irritants - that are readily available. Indeed, a number of infrasound technologies are currently registered with the US Patents Office. These include noise generators and transmitters, consciousness-altering machines and nervous system excitation devices - the list is growing all the time. .

In 1995, $41 million was spent on non-lethal weaponry in the US and there is growing interest in the technology. Many US police forces, concerned with the control of civil unrest, believe that infrasound has an advantage over tear gas as it can be controlled much more easily. The effectiveness of infrasound has even received the backing of the Pentagon, who in a recent document, claimed that high-power infrasound could leave an enemy incapacitated by nausea. New advances in infrasound weaponry suggest that military scientists are becoming more and more adept at harnessing ultra-low frequencies. A device currently under development is said to combine an infrasound device with a strobe light, and is capable of inducing extreme epileptic fits and complete sensory disorientation. Yet despite all the evidence, military authorities continue to deny any involvement with infrasound, and the actual nature of research remains shrouded in secrecy. Some have even claimed that the alleged properties of infrasound are far from proven. Recently, German physicist Jurgen Altmann claimed that, having studied the properties of infrasound, he found no evidence that it has any of the adverse effects reported. This view has been echoed by Lieutenant Colonel Martin N. Stanton of the US Army, who apparently found infrasound weapons of little use while based in war-torn Somalia as part of the US peacekeeping force. Stanton questions the effectiveness of such weapons, claiming that riot-control troops are just as susceptible to the effects of infrasound as rioters. Nevertheless, such scepticism does not appear to have affected those engaged in the production of infrasound weapons. In 1999, Maxwell Technologies of San Diego applied to patent a new potentially lethal infrasound weapon. The device, designed to control hostile crowds or disable hostage takers, is said to work a cross a wide range of frequencies and is highly directional. The company says it is capable of affecting people up to 100 metres away and can allegedly cause eardrum rupture at 185 decibels (dB), pulmonary (lung) injury at 200dB and death at 220dB.

Deadly Potential
These and other developments suggest that infrasound weapons are far from a pipe dream. With the need to control an ever growing population, it seems likely that, even if it hasn't been used already, the potential power of infrasound will be utilized in some form or other in the future. And with more devices being patented all the time, that day may be sooner than we think. .

Case: Wired by Sound
Aside from the threat of infrasound weaponry, a subtler danger may lie in the low levels of infrasound that surround us on a daily basis. Within the everyday items of urban technological living are numerous devices that are known to produce infrasound. Machinery such as cars, heating systems and trains all produce ultra-low frequencies, and often city-dwellers complain of illnesses that may be triggered by such 'infrasonic pollution'. The effects can vary from sleep disturbance and irritation to suicidal tendencies, but could this, as some have suggested, be a deliberate oppression of the masses? Whilst this is unlikely, in the mid-1970s, concerns over the effect of infrasound (above) under the alarmist headline: The Low Pitched Killer: Can Sounds of Silence be Driving Us All Silly? Public worries were duly intensified and, during this period, one in-depth newspaper report apparently received 800 responses from people claiming to have suffered as a result of low levels of infrasound.