Some researchers at the University of Michigan think they may have come up with an explanation. It doesn't completely exonerate the Cuban government, rather the contrary. If correct, these scientists do provide a slightly less sinister explanation, however.
"Did These Computer Scientists Solve the Cuban ‘Sonic Attack’?"
A technical report from the University of Michigan offers a stunningly simple theory for the source of the Cuban “sonic attack”: a pair of eavesdropping devices too close to each other and tripping the ultrasound that ironically was supposed to make their presence quiet.
More importantly, it might not have been done with malicious intent.
“It doesn’t prove it’s the cause,” Kevin Fu, an associate professor at the University of Michigan and one of the co-authors of the study, cautioned. “It’s a correlation. But to us, it seems like a strong correlation.”
A recap: Last September, the State Department recalled 21 American employees from the U.S. embassy in Havana. These employees, along with three Canadians, reported dizziness, cognitive difficulties, headaches, and hearing loss, among other medical issues, according to an official statement made by Secretary of State Rex Tillerson. The victims of what was being termed a “sonic attack” reported hearing a high-pitched sound that made them physically ill.
In December, the AP reported that patients showed “unprecedented” neurological damage, with hearing loss, memory problems, and cognitive issues. This prompted further speculation as to what the “sonic terror” device was: Some thought it was an advanced Russian tool that was sneaked into the embassy; others thought it was poisoning. A Cuban panel of scientists thought the “psychogenesis” was brought about by stress.
To add to the confusion, doctors weren’t sure either what was going on. In a preliminary report published in JAMA, physicians treating the patients could only say a “novel mechanism” caused the neurological damage. A companion report in JAMA published last month came to no conclusion as to what could possibly be causing the neurological damage patients had suffered.
Fu and his team were working on a project testing the audibility of ultrasound in another project, but the AP video caught their eye.
“At the time, people were talking about ultrasound [being a theory as to what the sound was],” Fu said. “But it didn’t make sense. Ultrasound is inaudible [to humans], and you wouldn’t hear it.”
But what if the ultrasound here got tripped up by an interruption—perhaps a pair of eavesdropping devices whose transmission got tangled over what was supposed to be an inaudible ultrasonic link but instead became audible?
Fu and his colleagues tested this theory by having an eavesdropping device record conversations that were then sent over to a surveillance team via ultrasonic link, which was supposed to be inaudible to the human ear. But Fu’s group also dropped another otherwise-inaudible ultrasonic device in the vicinity of the first device, creating interference—what’s known as “intermodulation distortion”—that could lead to the 7 kHz tinny sound the team replicated and identified in the AP’s sound recording.
“It doesn’t prove that this is what happened in Cuba,” Fu cautioned. “But it does show that there’s a reasonable probability that it’s an accident rather than someone causing harm [intentionally].”