The mysterious "ultrasonic weapon" complained about by the US Embassy in Cuba does not exist in reality - it turned out to be a byproduct of several harmless listening devices, say scientists from the US and China.
“Even if ultrasound really deafened the embassy staff and damaged their brains, it was not the 'ultrasonic weapon' that was the source of it, but the cross-distortion resulting from the interaction of the two ultrasonic signals that generated a lot of unpleasant noises. In other words, no one set a goal to harm the health of diplomats - everything happened by chance,”the authors of the article write.
Resident error
In August last year, another international spy scandal broke out - the staff of the US Embassy in Cuba accused the authorities of the island of being subjected to covert "ultrasonic attacks" using some new forms of weapons. These attacks, as the American media wrote at the time, began in December 2016 and continued until early September 2017, deafening and causing serious health problems for at least 24 diplomats.
As the victims of this "attack" themselves reported, they constantly heard very loud, harsh sounds, similar to the clang and grinding of rubbing metal structures, which caused them very sharp pain when they were at certain points either at home or inside the embassy. Living in such an environment deprived many of them of their hearing, and some diplomats complained of constant nausea and inability to remember certain words and information.
Such statements immediately drew a lot of criticism among intelligence officers and scientists - the human ear is not able to hear ultrasound, and the ultrasonic waves themselves, in principle, cannot cause the damage to brain tissue, which doctors who examined the victims of the "attack" later told about.
As a physicist from MIT put it then, this could only happen if diplomats dived headlong into a pool, whose walls were covered with powerful ultrasound emitters. Nevertheless, the US authorities did not abandon such theories and promised to deal with the situation and punish those responsible by starting an investigation, in which Russia and Cuba immediately became the main suspects.
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Kevin Fu, a physicist at the University of Michigan at Ann Arbor (USA), and his colleagues at Zhejiang University (China) analyzed examples of "ultrasonic vibrations" recorded on a smartphone by the embassy staff and published in the media, and found out how this "weapon" could have been born.
Experimental spyology
As physicists note, they were primarily interested in how ultrasound beams could generate sounds that a person can hear. According to them, this is possible only if these waves interacted with some other objects, while generating other types of acoustic vibrations.
Guided by this idea, the scientists analyzed the spectrum of the recording and came across its unusual feature. According to them, these sounds are similar in structure to the so-called cross-distortion, which occurs when two or more signals are mixed.
Their source, as further experiments of physicists showed, most likely were hidden microphones and other equipment that used narrow ultrasound beams to transmit the recorded sound to Cuban intelligence officers or some other spies.
A prototype of the 'ultrasonic weapon' that the US accused Cuba of using / Yan et al. / University of Michigan 2018.
When such beams crossed, they generated a lot of noise and distortion near the point where such a collision occurred, as well as inside the microphones themselves and in the inner ear of a person. They were what Fu and his colleagues believe were heard by the embassy staff.
Such eavesdropping devices, according to physicists, are not something prohibitively complicated - they managed to create their own "spy network" and reproduce the sounds that occur when interference appears in the ultrasonic signal, using ordinary smartphones and parts from a radio store.
Moreover, as physicists joke, they managed to improve this "ultrasonic weapon" by learning to control the volume of sounds generated by noise and use them to convey meaningful information. All this, according to scientists, suggests that the spy scandal in Cuba was caused by relatively harmless eavesdropping devices, and not by a mythical sonic weapon.
