Some background information:
"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.
..
During the Cold War, science was the focus of intense super-power
rivalry. Even areas like mind control were explored, amid fears of the
other side getting an edge - and this included microwaves.
Prof Lin was shown the Soviet approach at a centre of scientific
research in the town of Pushchino, near Moscow. "They had a very
elaborate, very well-equipped laboratory," Prof Lin recalls. But their
experiment was cruder than his. The subject would sit in a drum of salty
seawater with their head sticking out. Then microwaves would be fired at
their brain. The scientists thought the microwaves interacted with the
nervous system and wanted to question Prof Lin on his alternative view.
Curiosity cut both ways, and US spies kept close track on Soviet
research. A 1976 report by the US Defense Intelligence Agency, unearthed
by the BBC, says it could find no proof of Communist-bloc microwave
weapons, but says it had learnt of experiments where microwaves were
pulsed at the throat of frogs until their hearts stopped. "
https://www.bbc.com/news/world-58396698