Scientists say recording of sound heard by U.S. diplomats in Cuba matches crickets

A strange sound heard by embassy workers who fell ill matches a Caribbean cricket, but the finding doesn't solve the mystery.</s>WASHINGTON — New research into a recording of a mysterious sound heard by U.S. embassy workers who fell ill in Cuba indicates that the high-pitched sound matches the chirp of a certain species of cricket.

Starting in late 2016, American diplomats and intelligence officers started reporting strange symptoms that developed after they experienced unexplained sounds and sensations in their homes in Havana.

Twenty-six Americans were eventually deemed by the U.S. to have been affected by what the government has called “specific attacks” on its diplomats leading to hearing, vision and cognitive problems.

Numerous recordings were made by workers who heard strange sounds in Cuba, and in October 2017, The Associated Press obtained and published one such recording, describing it as a “high-pitched whine” that “sounds sort of like a mass of crickets.”

Now a pair of biologists has studied the recording and say that it closely matches the calling song of the Indies short-tailed cricket, found in parts of the Caribbean but not known to exist in Cuba.

The study by researchers Alexander Stubbs of the University of California Berkeley and Fernando Montealegre-Z of the U.K.’s University of Lincoln adds to the ongoing mystery about what happened to the U.S. embassy workers, but does not answer the central question: how they ended up with conditions that the State Department says includes hearing loss, memory issues and mild traumatic brain injury.

“It focuses narrowly on what was heard on the recording,” Stubbs told NBC News. After the initial cases in Cuba were detected, U.S. diplomats posted there were encouraged to record strange sounds that they heard and in some cases were given recording devices by the government.

Last year, an interim FBI report said that sound waves alone couldn’t have caused the damage, raising the possibility that whatever sound the diplomats heard was not the direct cause of their injuries. Some investigators have suggested that the sound could have been the byproduct of something else that caused the damage or beamed at the diplomats as a decoy to obscure another type of technology.

“The fact that the sound on the recording was produced by a Caribbean cricket does not rule out the possibility that embassy personnel were victims of another form of attack,” Stubbs and Montealegre-Z wrote in their paper, which has not yet been peer-reviewed or published in a scientific journal.

Crickets, when they produce sound with their wings, create a “distinct acoustic signature” that can be measured for several characteristics, the researchers wrote — similar to how each person’s fingerprint is unique. Using technology that creates visual representations of sound signals, they were able to study characteristics such as pulse repetition rate, oscillations per pulse and duration.

“The way that they produce their sound, the wing decelerates through each sound pulse, which allows you to see the frequency change through each sound pulse,” Stubbs said in an interview.

Cuba has adamantly denied any knowledge of or involvement in any attacks in U.S. diplomats. In 2017, Cuban experts who had studied recordings of the sound provided to Cuba by the U.S. government said they’d determined they were very similar to the sounds of cicadas and crickets that live along Cuba’s coast.

The Indies short-tailed cricket, known scientifically as anurogryllys celerinictus, has been found previously in Jamaica, Grand Cayman and the Florida Keys, but isn’t known to exist in Cuba. Still, a similar type of cricket is found in Cuba, and the researchers hypothesize that it’s possible that the Indies short-tailed cricket is present there, too.

At first, the researchers studying the AP recording found that the pulse structure was “unlike any natural insect source.” But they suspected that was because the diplomats had recorded the sound while indoors, where the recording might picked up echoes from the walls and floor, as opposed to recorded outside “in the field.”

To test that theory, they took a recording of the Indies short-tailed cricket and played it indoors on a loudspeaker. They then recorded it again and found that it now matched the pulse structure seen in the recording from Cuba.

Previous studies of the recordings, which have also been extensively studied by the U.S. military, have come to different conclusions. Last year, engineers at the University of Michigan who studied the same AP recording in a lab determined that the sound could have been the unintended side effect of poorly built ultrasonic eavesdropping devices that combined to create audible sound heard by the diplomats.</s>At first, it sounded like a plot ripped from the pages of a Tom Clancy political thriller. But it turns out the mysterious noise that tormented U.S. diplomats serving in Cuba may have more in common with a David Attenborough nature documentary. 



Scientists studying recordings made by diplomats of the unusual high-pitched sounds, which reportedly triggered symptoms such as headaches, nausea and hearing loss for over two years, say the source is the common Caribbean cricket.

"There’s plenty of debate in the medical community over what, if any, physical damage there is to these individuals," Alexander Stubbs of the University of California, Berkeley told The New York Times. "All I can say fairly definitively is that the [Associated Press]-released recording is of a cricket, and we think we know what species it is."

Stubbs, along with co-author Fernando Montealegre-Z of the University of Lincoln in England, recently submitted a paper outlining both their analysis of the strange recordings and their conclusions that it belongs to the incessant mating call of the Indies short-tailed cricket.

Normalized amplitude spectrum of potential sound sources compared to the recording published by the Associated Press. (Photo: Alexander Stubbs/Fernando Montealegre-Z)

"As shown here, the calling song of the Indies short-tailed cricket (Anurogryllus celerinictus) matches, in nuanced detail, the AP recording in duration, pulse repetition rate, power spectrum, pulse rate stability, and oscillations per pulse," they write. "The AP recording also exhibits frequency decay in individual pulses, a distinct acoustic signature of cricket sound production."

While the scientists initially found small differences in comparing the acoustic signatures, they soon fixed the issue by recording the sound of the short-tailed cricket in the same way the diplomats would have heard it: from within a house. A near-perfect match of the crickets' piercing trill, a mind-numbing song you can play for yourself here, was then achieved.

"They're incredibly loud," Stubbs told the Times. "You can hear them from inside a diesel truck going forty miles an hour on the highway."

While they believe they've confirmed the source of the recording published by the Associated Press, the scientists nonetheless don't have answers for why the sounds triggered such harmful symptoms in the diplomats.

"Although the causes of the health problems reported by embassy personnel are beyond the scope of this paper, 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 conclude.

Crickets suspected in 'sonic attacks' on U.S. diplomats in Cuba

The bizarre, unexplained sounds that harmed American diplomats working in Cuba may have come from the Indies short-tailed cricket.</s>Scientists say a mysterious buzzing that was linked to a possible sonic attack of U.S. embassy members in Cuba in 2016 and 2017 may have been caused by crickets, according to new findings by a pair of scientists.

A recording obtained by The Associated Press was reportedly analyzed by scientists who determined it matched the sounds of the Indies short-tailed cricket Anurogryllus celerinictus.

The sounds were described by diplomats as "piercing sounds," "buzzing" and "grinding metal." It was reportedly associated with symptoms such as vertigo, dizziness, vertigo, and ringing in the ears. There were concerns by U.S. officials that the diplomats were the target of an attack. People affected reportedly suffered problems with concentration, balance, eyesight, hearing, and memory, among other things.

A British and an American scientist determined the cricket chirps matched "in nuanced detail, the AP recording in duration, pulse repetition rate, power spectrum, pulse rate stability, and oscillations per pulse." Their findings, however, have not been peer reviewed.

Click here to listen to what Anurogryllus celerinictus sounds like, according to the University of Florida Entomology and Nematology Department.

"While the temporal pulse structure in the recording is unlike any natural insect source, when the cricket call is played on a loudspeaker and recorded indoors, the interaction of reflected sound pulses yields a sound virtually indistinguishable from the AP sample. This provides strong evidence that an echoing cricket call, rather than a sonic attack or other technological device, is responsible for the sound in the released recording," the scientists found.

Despite the findings, the U.S. State Department and federal investigators are reportedly still investigating the cause. Cuba has denied being involved in any attack.</s>The mysterious high-pitched buzzing sound associated with suspected "sonic attacks" on U.S. diplomats in Cuba may have actually been caused by crickets, according to a report published Friday in a biology journal.

The strange incidents began in late 2016 when U.S. embassy personnel began seeking medical care for hearing loss and ear-ringing that was eventually linked to weird noises or vibrations — circumstances that initially led investigators to suspect the diplomats were victims of malicious "sonic attacks."

The Associated Press released audio in October 2017 of the high-pitched sounds heard in Havana, and that audio was then analyzed by a pair of researchers at the University of California, Berkeley and the University of Lincoln, in the United Kingdom.

CUBA CITES LACK OF EVIDENCE IN MYSTERIOUS SONIC ATTACKS ON DIPLOMATS

The findings, published Jan 4. in the preprint journal BioRXiv, determined the recording matched the sounds of the Indies short-tailed cricket known as Anurogryllus celerinictus, which is native to Cuba.

The scientists, Alexander Stubbs and Fernando Montealegre-Zapata, noted the sounds of the crickets matched "in nuanced detail, the AP recording in duration, pulse repetition rate, power spectrum, pulse rate stability, and oscillations per pulse."

The findings, which LiveScience reported were not yet peer reviewed, also noted the AP recording exhibited "frequency decay in individual pulses, a distinct acoustic signature of cricket sound production."

"While the temporal pulse structure in the recording is unlike any natural insect source, when the cricket call is played on a loudspeaker and recorded indoors, the interaction of reflected sound pulses yields a sound virtually indistinguishable from the AP sample," the scientists noted. "This provides strong evidence that an echoing cricket call, rather than a sonic attack or other technological device, is responsible for the sound in the released recording."

"HEALTH ATTACKS" ON U.S. DIPLOMATS IN CUBA STILL A MYSTERY SAYS NEW REPORT

The U.S. says that, since late 2016, 26 people associated with the embassy in Havana suffered problems that include dizziness, ear pain and ringing, and cognitive problems such as difficulty thinking. The U.S. has not definitively said what caused the incidents, although initial speculation centered on some type of sonic attack.

The AP has reported an interim FBI report in January 2017, however, found no evidence sound waves could have caused the damage.

The health mystery damaged U.S.-Cuba relations, with embassy staff pulled from the island and Americans warned not to visit. In an August 2018 advisory, the State Department warned Americans to "exercise increased caution" due to the unexplained incidents.

Cuban officials have adamantly denied involvement and even used a prime-time special, "Alleged Sonic Attacks," in October 2017 to point to a lack of evidence by U.S. officials.

US EMBASSY WORKERS IN CUBA FOUND TO HAVE BRAIN ABNORMALITIES, REPORT SAYS

Officials with Cuba's Interior Ministry said at the time that U.S. investigators had presented them with three recordings made by presumed victims of sonic attacks and that analysis of the sounds showed them to be extremely similar to those of crickets and cicadas that live along the northern coast of Cuba.

The program's narrator said unnamed "North American researchers" had also found some cicada and cricket noises could be louder than 90-95 decibels -- enough to produce hearing loss, irritation and hypertension in situations of prolonged exposure.

In December, a group of doctors revealed the American diplomats affected by the sounds showed damage in the inner ear shortly after they complained of weird noises and sensation. The detailed findings were published in a medical journal Laryngoscope Investigative Otolaryngology.

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Researchers examined 25 people who reported hearing a piercing noise or experiencing a sensation of pressure before their symptoms began. The patients failed a variety of tests that detect inner-ear problems associated with balance, what's called the vestibular system — although there were no pre-symptom medical records to compare the tests to.

Testing of 10 other people who were in the same building at the time of the incidents found they were fine, according to Dr. Michael Hoffer of the University of Miami Miller School of Medicine.

"What caused it, who did it, why it was done — we don't know any of those things," Hoffer told the Associated Press at the time.

Fox News' Jennifer Earl, Nicole Darrah and the Associated Press contributed to this report.</s>In late 2016, dozens of staffers at the U.S. Embassy in Cuba fell sick after reportedly hearing mysterious noises in their hotels or homes. Afterward, they reported severe physical symptoms, including vertigo, headaches, ear pain and even cognitive difficulties and hearing loss.

Researchers obtained a recording of the sounds captured by embassy workers in Cuba, and analysis of the acoustic signal revealed striking similarities to insect calls. Further investigation identified the sounds as the call of the Indies short-tailed cricket (Anurogryllus celerinictus). [Flying Saucers to Mind Control: 22 Declassified Military & CIA Secrets]

The findings, which have not yet been peer-reviewed, were presented at the annual meeting of the Society of Integrative and Comparative Biology in San Francisco, and were published online Jan. 4 in the preprint journal BioRXiv.

In the months after alleged attacks occurred, some embassy personnel reported symptoms so debilitating that they were recalled from their posts in Havana, and returned to the U.S. for medical evaluation. American officials initially claimed that a secret sonic weapon was to blame, and Cuban diplomats were expelled from the U.S. in retaliation, Live Science reported in August 2017. (Other theories, such as microwave weapons, were also proposed.)

In the new study, researchers reviewed a recording of the potential offending sound — a "buzzing" at a frequency of 7 kHz, or 7,000 cycles per second, captured by embassy workers and released by the Associated Press. The researchers found that the buzz in the recording strongly resembled the song of the Indies short-tailed cricket, "in duration, pulse repetition rate," and in other aspects of the sound pulses, they reported in the study.

But there was one notable difference. Pulses in the AP recording were irregular, while field recordings of wild crickets captured more uniform trills. One explanation could be that the Cuban recording was recorded indoors, where sound could rebound off ceilings, floors and walls to create a complex echo chorus in an irregular rhythm, according to the study.

To test that hypothesis, the researchers played back recorded cricket calls through a speaker indoors and recorded the results. They found that when echoes were added, as the sound ricocheted between flat surfaces, the pulse structure of the recordings matched the one in the AP recording from Cuba.

"This provides strong evidence that an echoing cricket call, rather than a sonic attack or other technological device, is responsible for the sound in the released recording," the researchers wrote. (The analysis explains only what was in this particular recording, something that may or may not have been related to the symptoms reported by embassy workers and others.)

The new study isn't the first to suggest that there was no "sonic weapon" behind the embassy workers' unusual symptoms. In February 2018, researchers documented the range of ailments suffered by 21 individuals who worked in the U.S. Embassy and reportedly fell ill in 2016 and 2017. They concluded that the symptoms simply didn't match those likely to be caused by weaponized sound waves, Live Science previously reported.

The findings suggest that experts need to look more closely at what may have caused these symptoms, "as well as possible physiological explanations unrelated to sonic attacks," the scientists wrote in the study.
• The 7 Biggest Mysteries of the Human Body</s>Beginning in late 2016, a mysterious illness befell U.S. diplomatic personnel and family members in Havana.

Specialists said the symptoms, described by those afflicted as “buzzing, grinding metal, piercing squeals and humming,” were similar to the brain dysfunction caused by concussions.

The U.S. government personnel in Cuba reported hearing these weird, loud sounds along with feelings of changes in air pressure in homes owned and maintained by the Cuban government and hotel rooms. Although there had been no history of head trauma, the symptoms reported were consistent with brain injury.

Some U.S. officials suspected the “health attacks” were intentional, perhaps perpetrated by the Cuban or Russian governments. But new research has implicated another culprit in the noise: Very loud crickets.

Scientists analyzed a recording of the sound reportedly related to the incidents released by The Associated Press in 2017 and found it matched the chirp of the Indies short-tailed cricket Anurogryllus celerinictus “in duration, pulse repetition rate, power spectrum, pulse rate stability, and oscillations per pulse.”

This particular kind of cricket is typically found in the Caymans, Florida Keys and Jamaica, but researchers Alexander L Stubbs of the University of California Berkeley, and Fernando Montealegre-Z of the University of Lincoln in England believe they may also be present in Cuba.

The researchers noted that the pulse structure of the AP recording initially didn’t match outdoor field recordings of the insects, but when the cricket call was played indoors, “the interaction of reflected sound pulses yields a sound virtually indistinguishable from the AP sample.”

They said their research, which has not yet been peer-reviewed, provides “strong evidence” that crickets produced the sound on the recording. However, their findings highlight the need for more rigorous research on what caused the diplomat’s ailments and does not rule out the possibility of another form of attack, according to the report.

The State Department created an expert panel to investigate the incident in July 2017 that determined the initial findings were most likely related to "neurotrauma from a non-natural source." The department recommended further investigation.

In response to the incidents in Cuba, the State Department expelled 15 Cuban diplomats from the Washington embassy and initially reduced the number of workers in Havana. These sharp reductions would later be made permanent due to health concerns. The State Department officials have told Congress that 26 embassy workers in Cuba were affected by the mysterious health incidents since it was first discovered in December 2016.

A team of specialists from the University of Pennsylvania’s Center for Brain Injury and Repair couldn’t determine the cause of the mysterious illness but found that the Havana patients “experienced persisting disability of a significant nature.”

The Cuban government insisted that it played no role in the attacks and worked with U.S. investigators to determine the cause of the ailments.</s>In all the noise that comprises our national news landscape these days, noise itself doesn’t often rise to the level of news.

That changed in 2016 when U.S. diplomats stationed in Cuba in October repeatedly reported hearing high-pitched sounds that were followed by hearing loss and other medical symptoms.

Fears arose that the Americans might be under some sort of sonic attack by persons or countries unknown. It was a big story, but over time it got lost in other news noise.

That ended this month when the noise ratcheted up. At the annual meeting of the Society of Integrative and Comparative Biology, UC Berkeley integrative biology Ph.D. student Alexander Stubbs and Prof. Fernando Montealegre-Zapata of the University of Lincoln in the U.K. put forward a study of a recording of the mysterious sounds and posted a preprint to the online repository bioRxive https://www.biorxiv.org/content/early/2019/01/04/510834.

Their determination: the high pitch heard by the diplomats was produced by the Indies short-tailed cricket (A. celerinictus).

It was a conclusion quickly picked up by the New York Times and zipped around the internet.

Stubbs and Montealegre-Z do not address the medical problems reported by the diplomats in their study; they just pointed out that the noise linked to those medical issues was, in fact, crickets.

“We are showing this recording is in no way dangerous,” Stubbs says. “These sounds may have nothing to do with these people. The whole narrative originally was sonic attacks and loud sounds with acute symptoms.”

Politically, 2016 was a big time in Cuba. The Obama administration had opened the U.S. embassy in Havana just a year earlier. In part because of the noise and health issues, U.S. Secretary of State Rex Tillerson greatly reduced the embassy’s staffing after the Trump administration took over in 2017. With personnel getting sick, and mysteriously so, the working hypothesis pointed toward some kind of sonic weapon.

One study published in the Journal of the American Medical Association reported that 20 embassy staffers showed signs of concussion, including cognitive deficiencies, and the study suggested a “directed energy” attack might have been responsible. This interpretation of the evidence is hotly debated in the medical community, however, and other researchers have suggested that psychogenic illness is more likely to blame.

One common thread in the staffers’ reports was a loud, piercing sound, which was recorded by U.S. personnel stationed in Cuba. A series of these recordings were analyzed by the U.S. government and given to both the Associated Press and the Cuban government.

There were investigations, both on the American and Cuban sides, and it was a major news story. But the source of the noise couldn’t be pinned down. The Associated Press put one of the recordings on the internet for all to hear, advising that the sound wasn’t believed to be dangerous if listened to in a short burst.

One hypothesis that made its way to the Daily Beast suggested that malfunctioning spy gizmos might be to blame for this sound while the New York Times had experts suggesting futuristic microwave weapons. The Cubans suggested the Jamaican field cricket (Gryllus assimilis), but its call sounds little like the recording released by the AP.

Stubbs, a grad student in professor Jimmy McGuire’s lab in the Museum of Vertebrate Zoology at Berkeley, does intensive fieldwork on reptiles and amphibians in tropical environments under McGuire’s guidance. And it was because of that fieldwork that Stubbs, after listening to the recording released by the AP, says, “It is the time I spent in the field as a Berkeley student both as an undergraduate and as a graduate student that made me think I had heard something like this before.”

Using the Singing Insects of North America database put together by Tom Walker at the University of Florida, Stubbs identified the culprit as the Indies short-tailed cricket (A. celerinictus), based on a match of the power spectrum of this species with the recording released by that AP.

Despite that match, the pulse structure of the AP recording did not match any of the field recordings in Walker’s database. The breakthrough, Stubbs says, came when he realized the difference could be accounted for by the fact that the recording was made near buildings or indoors. Near a structure, sound pulses would be reflected, creating echoes that would obscure the cricket’s typical sound pattern. When he played the A. celerinictus call on a speaker indoors, it was a nearly perfect match with the recording the U.S. diplomats made in Cuba. The Indies short-tail cricket is common on Grand Cayman, an island where Stubbs has spent time researching lizards for his project on reptilian vision.

Stubbs then collaborated with Montealegre-Z in the U.K. to show that the recording had a characteristic frequency drop over each sound pulse that matches the detailed biomechanics of cricket calls. It is this frequency drop in each sound pulse that most conclusively shows this recording is of a cricket, and not any other artificial or natural source, he says.

Asked how they can be so sure that the species identified in their report is really correct, Stubbs says, “No other known continuously calling cricket has a wing stroke rate of 180 per second. We can definitively say this recording is of a cricket, and we are pretty sure we know what species it is.”

After last Friday’s New York Times story, Stubbs has been interviewed by the BBC’s World Service, Newsweek and the Canadian Broadcasting Corporation’s As It Happens program. Among others. On Monday, Stubbs had a list of 150 emails from various media organizations asking for comment.

“It is amazing how much interest has been generated just from our preprint,” Stubbs said, adding “but we look forward to having it published in a peer-reviewed journal shortly.”

Amazingly, as pointed out in a recent article in The Atlantic, this is but one instance of biological phenomena causing people concern. In the Bay Area, the “Sausalito hum” that famously disturbed residents of houseboats in the North Bay in the 1980s was found to be the amorous call of the toadfish. The 1981 “yellow rain” incident came about when the United States accused the Soviet Union of providing communist fighters in Southeast Asia with chemical weapons that were later found to be the feces of giant bees.

“I really hope that this, the Sausalito hum and the yellow rain debacle serve as reminders that understanding our natural and biological world serves a useful purpose for humanity,” says Stubbs.

What was it, then, that produced the medical symptoms? Stubbs says he does not know. He does know a cricket didn’t do the damage. And he hopes this study can inform the dialogue going forward.</s>MIAMI - The mystery of the sonic weapon that is allegedly to blame over the health problems U.S. and Canadian government employees reported suffering after working in Havana has yet to be solved. And while the U.S. State Department's investigation on the alleged sonic attacks is still ongoing, a couple of scientists said the sound released as evidence was just crickets.

Fernando Montealegre-Zapata of the University of Lincoln in the United Kingdom, and Alexander Stubbs of the University of California in Berkeley both believe the audio sample the Associated Press released in 2017 released as evidence "exhibits frequency decay in individual pulses, a distinct acoustic signature of cricket sound production."

When the AP released the audio of "a recording of what some U.S. Embassy workers heard in Havana," the U.S. Navy did not respond to requests for comment, and the State Department didn't comment on the tape’s authenticity.

The two scientists believe their research showed the sound could be the call of the Indies short-tailed cricket, also known as the Anurogryllus celerinictus. This conclusion on the sound did not look at the reports by doctors who discovered brain abnormalities in the patients returning from Cuba.

The AP reported the recording was played for workers at the U.S. Embassy to teach them what to listen for, said several individuals with knowledge of the situation in Havana.

"I’ve met with the victims. I’ve met with their families," former Secretary of State Rex Tillerson said during an interview with the AP early last year. "I’m concerned about their health and wellbeing."

The scientists who have studied the symptoms of the medically confirmed cases haven't had controversial results. A study published last month reported the symptoms 25 people reported were similar to a "mild traumatic brain injury following blast exposure or blunt trauma."

Last year, another study published in the medical journal JAMA described the symptoms of 21 people who sought medical attention for symptoms that included headaches, memory, eyesight and hearing loss. Three required hearing aids.

The FBI report, which wasn't public, ruled out the U.S. State Department's sonic weapon theory.

Cuban officials have denied having a role behind the reported sonic attacks.

Copyright 2019 by WPLG Local10.com. The Associated Press contributed to this report. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.</s>Noise reported by US diplomats in Cuba not of weapons but insects

WASHINGTON: 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 wingstroke 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 theorising about mass hysteria.

The United States has not accused Cuba — with which former president Barack Obama normalised relations — of attacking the diplomats.

But President Donald Trump’s administration has blamed Cuba for failing to protect them.
Two biologists who analysed a sound recording obtained by the Associated Press in 2017, say that it closely matches the calling song of the Indies short-tailed cricket, a species not known to exist in Cuba.