ANN ARBOR, Mich. - It's an international incident that all but disintegrated America's relationship with Cuba, as American diplomats fell physically ill.
Some even suffered hearing loss and brain injuries thanks to some kind of sonic interference nobody could explain.
Many people have tried to figure out what was going on, and some University of Michigan minds might have found an unexpected answer.
Was it some sort of ultrasonic spy weapon that gave American diplomats concussions? That's what the FBI suspects and wants to figure out. But on a whim, a U fof M computer science and engineering processor took on the project and has a surprising answer.
Diplomats faced an annoying metallic sound. Some could hear it, but some of the older ones couldn't. There's a recreation based on a five-second clip the Associated Press recorded at the American Embassy in Cuba.
The case intrigued associate professor Kevin Fu.
"We were a little skeptical about claims of a sonic weapon," Fu said.
He reverse engineered the AP snippet and recreated it to examine how ultrasonic sound waves could happen.
"Just two ultrasonic signals colliding in the air can cause the same kind of characteristics," Fu said.
He built an electronics setup with a graphic equalizer to see the sound. A thin spike on the right shows a hurtful noise.
"It just makes sense to me that a sort of incompetence might make more sense than malice," Fu said.
Fu said automatic light switch sensors use ultrasound, as do some kinds of pest repellents.
"If there was, say, an eavesdropping device that was trying to spirit away some information over an ultrasonic, inaudible channel, if that happened to collide with one of these other systems, it could have produced these audible byproducts," Fu said.
The FBI is still investigating. The U.S. has pulled its diplomats from Cuba unless they are involved in the case, and Cuba's diplomats were sent home.
Fu sent his information to the State Department. He hasn't heard from them and said he's not expecting to.
You can view the full technical report below:
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