A noise heard by US diplomats in Cuba who suffered mysterious brain injuries came not from technological weapons but local crickets, a new study suggests.
In late 2016, US diplomats in Havana began to report ear pain and other symptoms from a high-frequency noise, leading Washington to withdraw half its embassy staff and to expel Cuban diplomats in retaliation.
But a study by two biologists assessed a purported recording of the noise and said it matched the mating song of the Indies short-tailed cricket found around the Caribbean.
The actual cause of the diplomats' ailments was outside the scope of the study, with the researchers not ruling out that the diplomats suffered a sonic attack at another point.
"While disconcerting, the mysterious sounds in Cuba are not physically dangerous and do not constitute a sonic attack," said the study by Alexander Stubbs, a graduate student at the University of California, Berkeley, and Fernando Montealegre-Zapata, a professor of sensory biology at the University of Lincoln in Britain.
"Our findings highlight the need for more rigorous research into the source of these ailments, including the potential psychogenic effects, as well as possible physiological explanations unrelated to sonic attacks," they wrote.
The researchers drew parallels to the 1981 yellow rain incident, when the United States accused the Soviet Union of deploying in Southeast Asia deadly chemical weapons—which some researchers later concluded to be droppings from bees.
In the Havana incident, the researchers studied a recording made by a US government employee that was sent to the US Navy for analysis and was later published by the Associated Press.
The researchers compared the recording with data from the Singing Insects of North America database run by University of Florida entomologist Thomas Walker, who found that the Indies short-tailed cricket had the fastest wing stroke rate of any known cricket that calls continuously.
The cricket's calling song matches the recording in "duration, pulse repetition rate, power spectrum, pulse rate stability, and oscillations per pulse," the study said.
The research was released last week and has not yet been peer-reviewed or published in an academic journal.
Around two dozen US diplomats and several Canadians reported dizziness, anxiety and mental fog—conditions that University of Pennsylvania researchers described as similar to concussions.
But other studies have dismissed the conclusion, with a paper in the International Journal of Social Psychiatry finding suspicious that no Cubans reported symptoms and theorizing about a mass hysteria.
The United States has not accused Cuba—with which former president Barack Obama normalized relations—of attacking the diplomats.
But President Donald Trump's administration has blamed Cuba for failing to protect them.
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