Hard evidence has been elusive, making the syndrome a battleground for competing theories. Some see it as a psychological illness, others a secret weapon. But a growing trail of evidence has focused on microwaves as the most likely culprit.
In 2015, diplomatic relations between the US and Cuba were restored after decades of hostility. But within two years, Havana syndrome almost shut the embassy down, as staff were withdrawn because of concerns for their welfare.
Initially, there was speculation that the Cuban government - or a hard-line faction opposed to improving relations - might be responsible, having deployed some kind of sonic weapon. Cuba's security services, after all, had been nervous about an influx of US personnel and kept a tight grip on the capital.
That theory would fade as cases spread around the world.
Short presentational grey line
But recently, another possibility has come into the frame - one whose roots lay in the darker recesses of the Cold War, and a place where science, medicine, espionage and geopolitics collide.
When James Lin, a professor at the University of Illinois, read the first reports about the mysterious sounds in Havana, he immediately suspected that microwaves were responsible. His belief was based not just on theoretical research, but first-hand experience. Decades earlier, he had heard the sounds himself.
Since its emergence around World War Two, there had been reports of people being able to hear something when a nearby radar was switched on and began sending microwaves into the sky. This was even though there was no external noise. In 1961, a paper by Dr Allen Frey argued the sounds were caused by microwaves interacting with the nervous system, leading to the term the "Frey Effect". But the exact causes - and implications - remained unclear.
In the 1970s, Prof Lin set to work conducting his experiments at the University of Washington. He sat on a wooden chair in a small room lined with absorbent materials, an antenna aimed at the back of his head. In his hand he held a light switch. Outside, a colleague sent pulses of microwaves through the antenna at random intervals. If Prof Lin heard a sound, he pressed the switch.
A single pulse sounded like a zip or a clicking finger. A series of pulses like a bird chirping. They were produced in his head rather than as sound waves coming from outside. Prof Lin believed the energy was absorbed by the soft brain tissue and converted to a pressure wave moving inside the head, which was interpreted by the brain as sound. This occurred when high-power microwaves were delivered as pulses rather than in the low-power continuous form you get from a modern microwave oven or other devices.
Prof Lin recalls that he was careful not to dial it up too high. "I did not want to have my brain damaged," he told the BBC.
In 1978, he found he was not alone in his interest, and received an unusual invitation to discuss his latest paper from a group of scientists who had been carrying out their own experiments.
https://www.bbc.com/news/world-58396698
In 2015, diplomatic relations between the US and Cuba were restored after decades of hostility. But within two years, Havana syndrome almost shut the embassy down, as staff were withdrawn because of concerns for their welfare.
Initially, there was speculation that the Cuban government - or a hard-line faction opposed to improving relations - might be responsible, having deployed some kind of sonic weapon. Cuba's security services, after all, had been nervous about an influx of US personnel and kept a tight grip on the capital.
That theory would fade as cases spread around the world.
Short presentational grey line
But recently, another possibility has come into the frame - one whose roots lay in the darker recesses of the Cold War, and a place where science, medicine, espionage and geopolitics collide.
When James Lin, a professor at the University of Illinois, read the first reports about the mysterious sounds in Havana, he immediately suspected that microwaves were responsible. His belief was based not just on theoretical research, but first-hand experience. Decades earlier, he had heard the sounds himself.
Since its emergence around World War Two, there had been reports of people being able to hear something when a nearby radar was switched on and began sending microwaves into the sky. This was even though there was no external noise. In 1961, a paper by Dr Allen Frey argued the sounds were caused by microwaves interacting with the nervous system, leading to the term the "Frey Effect". But the exact causes - and implications - remained unclear.
In the 1970s, Prof Lin set to work conducting his experiments at the University of Washington. He sat on a wooden chair in a small room lined with absorbent materials, an antenna aimed at the back of his head. In his hand he held a light switch. Outside, a colleague sent pulses of microwaves through the antenna at random intervals. If Prof Lin heard a sound, he pressed the switch.
A single pulse sounded like a zip or a clicking finger. A series of pulses like a bird chirping. They were produced in his head rather than as sound waves coming from outside. Prof Lin believed the energy was absorbed by the soft brain tissue and converted to a pressure wave moving inside the head, which was interpreted by the brain as sound. This occurred when high-power microwaves were delivered as pulses rather than in the low-power continuous form you get from a modern microwave oven or other devices.
Prof Lin recalls that he was careful not to dial it up too high. "I did not want to have my brain damaged," he told the BBC.
In 1978, he found he was not alone in his interest, and received an unusual invitation to discuss his latest paper from a group of scientists who had been carrying out their own experiments.
https://www.bbc.com/news/world-58396698
