It was a scene straight out of “Star Trek,” according to the New York Times. While stationed in Havana, Cuba in late 2016, U.S. Embassy workers and their families at home and in hotel rooms heard a powerful, high-pitched sound and, with it, felt a high-pressure sensation. For some, problems with hearing, headaches, and cognition followed. The symptoms were serious enough to warrant evacuation from the country, generate a fair amount of diplomatic upheaval, and cause observers worldwide to scratch their heads and wonder if something truly was rotten in the city of Havana.
More than two years since the incidents began, United States-Cuba relations haven't recovered, and speculation continues about who would carry out the so-called “sonic attacks.” Cuba, a rogue faction there, Russia, and even North Korea have been floated as possible culprits.1 As well, the inevitable questions of why, and exactly how, the attacks were carried out also exist.
But over the past year, more details about the strange episodes—which occurred in Havana through early 2017 (and apparently in Guangzhou, China, in 2018, although the U.S. government has not officially linked the cases)—and their effect on the people who experienced them have begun to emerge.2,3 But instead of fitting together soundly, investigation updates are providing more twisty-turny pieces to this still-unsolved puzzle.
ACUTE AND CHRONIC SYMPTOMS
When a tight-knit community suddenly experiences similar symptoms of mysterious origin, collective delusion is a natural suspicion. Consequently, when news of the phenomenon in Havana went public, many onlookers wondered both silently and aloud whether it was a case of mass hysteria.
In February 2018, a report4 published online in JAMA by a team at the University of Pennsylvania in Philadelphia, which had evaluated nearly two dozen of the patients six months after their exposure to the sound, addressed this concern. Judging from the chronic symptoms observed in the patients, no one was imagining anything, the team said.
“Several of the objective manifestations consistently found in this cohort (such as oculomotor and vestibular testing abnormalities) could not have been consciously or unconsciously manipulated,” wrote Randel L. Swanson II, DO, PhD, and colleagues.4
The report described chronic concussion-like symptoms experienced by the patients: cognitive symptoms plagued 81 percent of the patients; balance, visual, and auditory dys-functions affected 71, 86, and 68 percent, respectively; sleep impairment, 86 percent; and headaches, 76 percent. Objective findings alone supported cognitive abnormalities in 76 percent of patients evaluated, vestibular problems in 81 percent, and oculomotor issues in 71 percent. The team also reported moderate to severe sensorineural hearing loss in three of the embassy employees.
Soon after it was published, however, the paper drew quick and blunt criticism.
“The JAMA article represents a case of poor neuro-psychology; clinically inappropriate and methodologically improper,” wrote Cortex editor and neuropsychologist Sergio Della Sala of the University of Edinburgh, UK, along with Roberto Cubelli of the University of Trento in Rovereto, Italy.5
In addition to the absence of raw scores for the objective assessments referenced in the JAMA study, the high thresholds and the psychometric approach the medical team used to identify objective impairment were questionable, argued the Cortex commentary, which appeared online on April 5, 2018.
“In conclusion, there is no evidence that the people assessed present[ed] with any cognitive deficit (to be linked or not with their stay in Cuba). Subjective cognitive symptoms cannot be supported by the reported data,” Della Sala and Cubelli wrote. “There is no ‘new syndrome’ to contemplate. Hence, the search for its cause is moot.”
Months passed, but in December 2018, experts at the University of Miami and University of Pittsburgh weighed in via another study, this one published online in Laryngoscope Investigative Otolaryngology.6 The University of Miami medical team, which included Hillary Snapp, AuD, PhD, was the first to evaluate embassy employees after their departure from Havana and, in its report, described the acute symptoms they saw, specifically, dizziness and/or cognitive complaints in every one of 25 symptomatic patients examined.
Patients reporting cognitive problems scored poorly on exams measuring memory and ability to multitask and absorb information amid background noise. “Everybody that I saw was quite disabled,” University of Miami neuropsychology director Bonnie E. Levin, PhD, told The New York Times.3
When patients wearing special goggles were strapped to a rotating chair in a darkened room to test their sense of up and down, eye movements recorded by the goggles indicated damage to two gravity organs in the ear. Lead author of the study Michael E. Hoffer, MD, told The New York Times that this otolithic abnormality had patients struggling to maintain their sense of balance as they went about their days—which in turn caused cognitive problems such as fatigue, forgetfulness, and emotional regulation.
“These people were injured,” said Hoffer, the director of the vestibular and balance program at the University of Miami. “We're not sure how. The injury resulted in ear damage and some trouble thinking.”3
THEORIES ON THE SOUND
With documentation of the acute and chronic symptoms experienced by patients now published in peer-reviewed journals, conjecture into what caused the symptoms—and what did not—persists. While the U.S. government still considers the episodes attacks, the FBI has ruled out a sonic weapon as a possible cause. Based on what they observed, the Penn team reportedly concurs.3
“We actually don't think it was the audible sound that was the problem,” JAMA study author Douglas Smith, MD, of the University of Pennsylvania, told CNN.2 “We think the audible sound was a consequence of the exposure.”
An analysis published online in the Journal of the Acoustical Society of America called theories of sonic attacks “speculative and premature.” In fact, “… everything in the evidence points away from labelling the events in Cuba and China as being ultrasonic attacks that caused brain injury,” wrote Timothy G. Leighton, PhD, professor of ultrasonics and underwater acoustics at the University of Southampton in the United Kingdom.7
But what about swapping the concept of sonic attacks for sonic delusions caused by an attack? Strikes using microwaves could explain the symptoms experienced by patients as well as the sound they perceived, experts told The New York Times.8 They cited a phenomenon known as the Frey effect—later termed the microwave auditory effect, then radio-frequency hearing—in which microwaves somehow trick the brain into hearing sounds that aren't actually there. (More than a half-century since the experiment that identified the neural sleight of hand, the mechanism behind it is still in dispute.) “I think that's a perfectly viable explanation,” scientist Allan H. Frey, now 83, told the newspaper. Scientific papers published in IEEE Microwave Magazine9 and Neural Computation10 agree.
“Each of the protean symptoms that diplomats report also affect persons reporting symptoms from radiofrequency/microwave radiation (RF/MW): sleep problems, headaches, and cognitive problems dominate in both groups. Sensations of pressure or vibration figure in each,” wrote Beatrice Alexandra Golomb, MD, PhD, a professor at the University of California, San Diego, in Neural Computation. “Both encompass vision, balance, and speech problems and nosebleeds. Brain injury and brain swelling are reported in both.”
An AP recording of the sound made by an embassy worker has, too, generated widespread attention.11 After analyzing the clip and conducting reverse engineering, computer scientists at the University of Michigan in Ann Arbor posited in a technical report that the sound could have been caused by interference after eavesdropping devices were placed too close together.12
“Our conclusion is that if ultrasound played a role in harming diplomats in Cuba, then a plausible cause is intermodulation distortion between ultrasonic signals that unintentionally synthesize audible tones,” the report explained. “In other words, acoustic interference without malicious intent to cause harm could have led to the audible sensations in Cuba.”
Meanwhile, integrative biology grad student Alexander Stubbs, University of California, Berkeley, and Fernando Montealegre-Zapata, PhD, University of Lincoln in England, hear crickets: Indies short-tailed crickets, to be exact. The pair maintain the AP sound lines up with the cricket call in duration, frequency drop, pulse repetition rate, power spectrum, pulse rate stability, oscillations per pulse “in nuanced detail.”13 Stubbs presented the findings at the annual meeting of the Society of Integrative and Comparative Biology in early January 2019.
“I'm confident the recording is of a cricket, and I'm fairly certain we know what the species is,” Stubbs told The Hearing Journal. “Most biologists are quite accepting of the idea it might be a cricket. And anyone who has spent a lot of time in the field thinks this is likely the case.
“The evidence is pretty overwhelming.”
To date, physicians and other medical specialists, biologists, computer scientists, and security experts have publicly shared thoughts on the sound and its cause. In a recent The Hearing Journal editorial, editorial advisory board chair Fan-Gang Zeng, PhD, expressed concern over the comparative hush among audiologists.
“The audiological community has remained surprisingly quiet even though both the source of the attack and its main symptoms are right up our alley,” observed Zeng.14 “Only when we are willing and able to tackle these tough questions can we demand and deserve the respect from our professional friends, trust from our patients, and payment from insurance companies.”
William A. Yost, PhD, a research professor in the spatial hearing laboratory at Arizona State University in Tempe, wondered whether the silence from audiologists is actually regrettable. Given that, to date, only two studies have described the symptoms experienced by embassy workers, audiologists have little data to go on.
“Even these studies do not provide a comprehensive set of measurements of auditory, vestibular, and cognitive function,” Yost wrote in a letter to the editor.15 “Such a lack of information means that commenting on the sonic attack would be mostly speculative. And, speculation may be harmful.”
In a follow-up interview, Yost expanded on his thinking.
“If you do not know much, speculation could harm or help, and the possible scenarios of what good or bad might happen are infinite,” he told The Hearing Journal. “What I am suggesting is great caution.”
For his part, Yost has a theory, although, for reasons previously stated, he shared it with some hesitation. He wonders if a compromised blood supply to the inner ear and subsequent brainstem damage to the stria vascularis—the metabolic engine of the inner ear—could be the cause of the hearing and vestibular dysfunction among affected embassy staff.
“Brainstem function, such as memory, requires good metabolic controls. Decades of work on tinnitus show that it is not necessary for there to be an actual sound for one to perceive a sound, even a loud sound in some cases,” he wrote. “It seems reasonable to assume that sudden metabolic damage throughout the brainstem might trigger a tinnitus-like perception of sound.”
As to what caused the compromised blood system, possibilities span sonic and concussive sources or even bacterial or viral pathogens.
Yost has heard from other audiologists who read his letter that his hypothesis has merit, although he said many have also pointed out issues with it. Those same colleagues have also questioned the cricket theory, as has Yost, particularly in light of the patients’ reported balance and cognitive symptoms after the sound exposure.
“All agreed,” Yost said, “that without more data and information, speculation is probably not a great idea.”
So, the puzzle sits, uncompleted. And after two years, pieces are still missing, leaving the possibly of a satisfying solution beyond the grasp of observers.
“Until more is known,” Yost observed in his letter, “I doubt that even the most erudite speculations will turn out to fully explain the mysteries surrounding these sonic attacks.”
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