Ultrasonic signals from faulty surveillance equipment is the likely cause of the unexplained illnesses of some two dozen American embassy officials in Havana last summer, according to University of Michigan researchers, Flipboard reported on Sunday.
The scientists said that while it is extremely unlikely that individual ultrasonic signals can harm people, multiple signals can clash with each other and produce a sound that is just low enough to be audible.
The researchers tested their theory by replicating the chirping from an AP video "using two ultrasonic emitters that combined tones, one at 25kHz and another at 180Hz," according to Flipboard. "That produced a similar-sounding 7kHz frequency with ripples of sound at an even 180Hz spacing."
The researchers themselves admitted that this theory does not rule out other possibilities for the mysterious illnesses, saying it was an attempt to find a reasonable explanation.
Last month doctors published the first detailed report on the illness, according to The Verge.
That report admitted the illness remains a mystery but said doctors are fairly certain it was not caused by a sonic weapon, as some claimed the Cuban authorities were using against the American diplomats.
The U.S. officials who experienced similar symptoms – including vertigo, nausea and hearing loss – said they first felt ill after hearing strange noises or feeling vibrations in their homes or hotel rooms, which led to speculation that Cuba was targeting the diplomats with some sort of attack.
However, there has been no proof of such allegations.
Earlier this month the Trump administration decided to make permanent its staff reduction at the embassy in Havana after it had recalled numerous diplomats due to the mysterious illness, VOA reported.
The State Department made the decision just before a six-month deadline required by law to either send the officials back to Cuba or make the reduction permanent.
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