There was a story that appeared in the news some time ago about a mysterious sound that was supposedly affecting US embassy personnel in Havana and creating such debilitating effects that it resulted in some of them deciding to come back to the US. There were allegations that Cuba was waging some kind of high-tech warfare against the US but the case for that was pretty thin, even allowing for the fact that there would be no motive for them to do so, since they are interested in improving ties with the US.

This long article by Tim Golden and Sebastian Rotella of ProPublica provides a detailed analysis of what exactly happened though it does not answer the key questions.

It was not until a Friday in late March that the diplomat realized he might be facing something more dangerous than bugs. At work that day, an embassy colleague with whom he was friendly took him aside and said he was leaving Cuba right away. A fit-looking man in his thirties, the colleague said he had just been in Miami, where medical specialists found he had a series of problems including a serious hearing loss. In late December, he said, he had been struck by a strange, disturbing phenomenon — a powerful beam of high-pitched sound that seemed to be pointed right at him.
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Even in a realm where secrets abound, the Havana incidents are a remarkable mystery. After nearly a year of investigation that has drawn on intelligence, defense and technology expertise from across the U.S. government, the FBI has been unable to determine who might have attacked the diplomats or how. Nor has the bureau ruled out the possibility that at least some of the Americans weren’t attacked at all. Officials who have been briefed on the inquiry described it as having made strikingly little progress in answering the basic questions of the case, with frustrated FBI agents reporting that they are running out of rocks to overturn.

What happened seems truly weird and has defied strenuous efforts to identify the problem, even though the Cuban authorities have cooperated in the investigation.