A team of computer scientists from the University of Michigan may have solved the mystery behind strange sounds heard by American diplomats in Havana, who later suffered a variety of medical disorders.
Professor Kevin Fu and members of the Security and Privacy Research Group at the University of Michigan say they have an explanation for what could have happened in Havana: two sources of ultrasound — such as listening devices — placed too close together could generate interference and provoke the intense sounds described by the victims.
And this may not have been done intentionally to harm diplomats, the scientists concluded in their study, first reported by the Daily Beast.
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Those who have followed the case closely say the new theory makes sense.
“This is a variation of what I have always thought,” James Cason, a former top U.S. diplomat in Havana, told el Nuevo Herald. “It explains the sonic part, that no one was spotted planting new devices inside the homes and doing it from the outside would require something huge.”
The health incidents — which took place between November 2016 and August 2017 at homes and two Havana hotels — were initially blamed on “sonic attacks.” The cause has perplexed the Department of State, the FBI and other U.S. agencies that have been trying to figure out just what made 24 intelligence officers, diplomats and relatives based in Havana ill. Many reported a variety of symptoms such as hearing loss, headaches, cognitive problems and other ailments that doctors said correlate with concussions.
University of Miami Dr. Michael Hoffer, who led the initial team of physicians who examined the victims, did not immediately respond to a request for comment on the Michigan report. The State Department said: “We still do not have a cause or source of the attacks. The investigation is ongoing.”
Most of the victims said they heard a shrill sound coming from a specific direction before experiencing the ailments.
Fu and his team used recordings of the sound obtained by The Associated Press and applied reverse-engineering to replicate what was heard by diplomats. By combining various ultrasound signals, they discovered that the resulting distortion produced an audible sound similar to what was heard in the original recording.
“When a second inaudible ultrasonic source interfered with the primary inaudible ultrasonic source, intermodulation distortion created audible byproducts that share spectral characteristics with audio from the AP news,” the university report said.
The Cuban government, which has independently investigated the incidents, has said that it found nothing suspicious in the recordings provided by U.S. agencies and that the sounds are similar to those produced by crickets and cicadas.
At first, Fu and his team did not find anything notable in the recording.
“We wondered for a moment if someone might be playing a joke on us,” they wrote in their report. But then they performed a procedure known as “AM demodulation,” and the resulting signal “sounds like an F1 engine.”
Fu’s theory, focused on ultrasound waves, would help explain why the victims described that the sound came from a specific direction. That is what 21 victims told a University of Pennsylvania medical team, according to an article published in the Journal of American Medical Association (JAMA).
“Ultrasound is more directional than audible sound and infrasound. Ultrasound can be focused on a certain area,” says the University of Michigan report.
So far, the United States has not found what caused the incidents that it has labeled “attacks on the health” of its diplomats. Cuba, for its part, has vehemently denied that it has attacked American personnel and has called the alleged attacks “science fiction.” If Fu’s theory is correct, Cuba’s response may be based on the premise that malfunctioning spy technology is not a form of aggression.
Several Canadian diplomats and their families also experienced similar symptoms, which generated more questions about why Cuba would venture to attack officials from Canada, the No. 1 source of tourism on the island.
Cason, who was in charge of the former U.S. Interests Section in Havana between 2002 and 2005, said that U.S. diplomats have lived for years in the same houses provided by the Cuban government and are aware that there are listening devices in them.
The theory that the incidents were due to malfunctioning devices and not staged attacks could explain why they only occurred in the homes of some diplomats and at two hotels in Havana, while not at the embassy.
“That cannot happen at the embassy in Havana because Cuban personnel are forbidden to enter higher floors,” where many diplomats have their offices, Cason said.
However, many questions remain unanswered: The most important is whether the ultrasound, the resulting sound distortion or both can cause the symptoms presented by the victims.
The doctors from the University of Pennsylvania could not explain the origin of the concussion symptoms, which several of the victims presented, although they ruled out other causes such as poisoning, a virus or collective hysteria.
More explanations on the cause are sure to surface.
“The JAMA report represents a collection of data from a partial sample of individuals seen at random times after an exposure, but not acutely. Our University of Miami team has provided a detailed description of how these individuals presented acutely,” Lisa Worley, a spokesperson at UM’s Miami Miller School of Medicine, said in a statement.
“This data is currently under peer review by a high-impact journal,” Worley said. “As the primary acute care providers in this case, we believe our work represents a high level of comprehensive detail that has not yet been reported. We look forward in the very near future to sharing our findings.”
In the JAMA article, doctors speculated that a new unknown source of “directional” character could cause brain damage. The authors also said there is no evidence that audible sounds could cause the symptoms. Although they did not speculate on what kind of technology may have caused the symptoms, they mentioned that microwaves can cause brain damage.
Many experts and American politicians have pointed to microwaves and to Russia as possible culprits for the attacks. This would imply that the Cuban government must have known whether foreign actors were involved. Other theories have suggested that a faction within the Cuban government could have acted on its own, which many observers believe is unlikely.
The Michigan report notes the lack of consensus and research on damage caused by ultrasound.
“The devices put in by the Cubans could have caused problems that no one knew could happen,” Cason said. “If this finally solves the mystery of sonic attacks, it is likely that Cubans will never admit it. They would have to recognize that they have eavesdropping devices everywhere, and that they will never say.”
Follow Nora Gámez Torres on Twitter: @ngameztorres