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| How could the 'sonic attack' on US diplomats in Cuba have been carried out? | How could the 'sonic attack' on US diplomats in Cuba have been carried out? |
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| The mysterious “sonic attack” on US diplomats based in Cuba raises questions about what form an acoustic weapon might have taken and the prevalence of such devices in the military. | The mysterious “sonic attack” on US diplomats based in Cuba raises questions about what form an acoustic weapon might have taken and the prevalence of such devices in the military. |
| The US State Department claims that the “attacks” started in autumn 2016 and ended in April this year and had affected at least 16 individuals. Officials said that the symptoms, including hearing loss, headaches and loss of balance, appeared to be the result of sophisticated devices operating outside the range of audible sound. No device nor any perpetrator has been discovered, however. | The US State Department claims that the “attacks” started in autumn 2016 and ended in April this year and had affected at least 16 individuals. Officials said that the symptoms, including hearing loss, headaches and loss of balance, appeared to be the result of sophisticated devices operating outside the range of audible sound. No device nor any perpetrator has been discovered, however. |
| A sonic weapon operating outside the human hearing range implies one emitting either very low (infrasound) or high (ultrasound) frequencies. In the second world war, the German military considered deploying an infrasound device, called the Wirbelwind Kanone (Whirlwind Cannon), aimed at knocking enemy bombers out of the sky using a vortex of sound. Targeted at people, infrasound can resonate with the stomach cavity, causing people to suddenly feel anxious or nauseated. | A sonic weapon operating outside the human hearing range implies one emitting either very low (infrasound) or high (ultrasound) frequencies. In the second world war, the German military considered deploying an infrasound device, called the Wirbelwind Kanone (Whirlwind Cannon), aimed at knocking enemy bombers out of the sky using a vortex of sound. Targeted at people, infrasound can resonate with the stomach cavity, causing people to suddenly feel anxious or nauseated. |
| However, low frequencies are difficult to target and the symptoms in the Cuban case do not appear consistent with infrasound attacks. | However, low frequencies are difficult to target and the symptoms in the Cuban case do not appear consistent with infrasound attacks. |
| Robin Cleveland, a professor of engineering science at the University of Oxford, said: “What’s probably happening in the Cuba situation, is ultrasonic – higher frequencies above above 20 kHz.” | Robin Cleveland, a professor of engineering science at the University of Oxford, said: “What’s probably happening in the Cuba situation, is ultrasonic – higher frequencies above above 20 kHz.” |
| Tim Leighton, professor of ultrasonics and underwater acoustics at University of Southampton, agreed: “If you want to produce a tight beam of energy that you can point at someone, ultrasound is the one to go for.” | Tim Leighton, professor of ultrasonics and underwater acoustics at University of Southampton, agreed: “If you want to produce a tight beam of energy that you can point at someone, ultrasound is the one to go for.” |
| There is good evidence that hearing loss can result from longterm exposure to ultrasound, based on studies of people working in factories where ultrasound is used to weld plastic parts. | There is good evidence that hearing loss can result from longterm exposure to ultrasound, based on studies of people working in factories where ultrasound is used to weld plastic parts. |
| Cleveland said that building an ultrasound emitter would not be hard. “You can buy transducers on the internet that emit these frequencies,” he said. “Anybody with a bit of engineering background could put one together.” | Cleveland said that building an ultrasound emitter would not be hard. “You can buy transducers on the internet that emit these frequencies,” he said. “Anybody with a bit of engineering background could put one together.” |
| A device the size of a kitchen matchbox could emit high enough amplitudes at close range to induce feelings of anxiety or difficulty concentrating. | A device the size of a kitchen matchbox could emit high enough amplitudes at close range to induce feelings of anxiety or difficulty concentrating. |
| However, putting together something powerful enough to affect hearing would be more challenging as it would require a large amplifier, may require a focused beam, and would need to be placed in the close vicinity of the target. High frequency sound does not travel well through barriers such as walls, curtains, or even human skin. | However, putting together something powerful enough to affect hearing would be more challenging as it would require a large amplifier, may require a focused beam, and would need to be placed in the close vicinity of the target. High frequency sound does not travel well through barriers such as walls, curtains, or even human skin. |
| “If you want to put a lot of power into it so you could produce a beam that could go through windows, it starts to look more like a suitcase,” said Leighton. “In order to generate hearing loss at 50 metres away, you’d be looking at a car-sized device.” | “If you want to put a lot of power into it so you could produce a beam that could go through windows, it starts to look more like a suitcase,” said Leighton. “In order to generate hearing loss at 50 metres away, you’d be looking at a car-sized device.” |
| Another ethical issue, specific to ultrasound weapons, is that they are difficult to target and tend to affect women and to a far greater degree children, more severely than middle-aged men. | Another ethical issue, specific to ultrasound weapons, is that they are difficult to target and tend to affect women and to a far greater degree children, more severely than middle-aged men. |
| US media reported this week that the medical records of some of the diplomats showed they had been diagnosed with mild traumatic brain injury. However, scientists were sceptical about the potential for an ultrasonic device to be capable of causing permanent brain damage. | US media reported this week that the medical records of some of the diplomats showed they had been diagnosed with mild traumatic brain injury. However, scientists were sceptical about the potential for an ultrasonic device to be capable of causing permanent brain damage. |
| “That’s a little harder for me to believe,” said Cleveland. “The sound would have to enter the brain tissue itself, but if you’ve ever had an ultrasound scan you’ll know they put gel on. If there’s even a tiny bit of air between the sound and your body it doesn’t get through.” | “That’s a little harder for me to believe,” said Cleveland. “The sound would have to enter the brain tissue itself, but if you’ve ever had an ultrasound scan you’ll know they put gel on. If there’s even a tiny bit of air between the sound and your body it doesn’t get through.” |
| One possibility is that this diagnosis is a result of to the range of symptoms experienced, which might include migraines, tinnitus, loss of balance and problems concentrating. However, these effects would normally be temporary. | One possibility is that this diagnosis is a result of to the range of symptoms experienced, which might include migraines, tinnitus, loss of balance and problems concentrating. However, these effects would normally be temporary. |
| Leighton, who has studied the safety of ultrasound and measures to avoid its potential adverse effects on humans, said he would like to see more “prosaic possibilities” such as drugs or poison ruled out before being persuaded of the sonic weapon theory. | |
| • This article was amended on 28 August 2017 to clarify the nature of Tim Leighton’s area of study. |