In late 2016, diplomats at the U.S. embassy in Havana complained of headaches and nausea due to a series of high-pitched, penetrating sounds.

Many suspected it might have been caused by an acoustic weapon. However, fresh analysis of the audio recording from the scene revealed that the "sonic attack" was not carried out by a Russian spy as initially thought by many, but by some short-tailed crickets called Anurogryllus celerinictus.

In a paper, a pair of researchers discussed the audio recording from the staff of the embassy and then released by the Associated Press in 2017. The analysis is available in the preprint server bioRxiv.org.

Sharp Noise Caused By Crickets

Fernando Montealegre-Zapata, a professor of sensory biology at the University of Lincoln and one of the researchers behind the paper, revealed that the piercing sound that diplomats heard were actually from male crickets calling out to females.

"The recording is definitively a cricket that belongs to the same group," he told The Guardian. "The call of this Caribbean species is about 7 kHz, and is delivered at an unusually high rate, which gives humans the sensation of a continuous sharp trill."

Montealegre-Zapata shared that he first-hand experienced the agonizing high-pitched drone of the crickets as a young child in South America. He said that he used to collect crickets and kept them in cages inside his own room.

Then, one night, he heard the loud noise from a similar species calling out for females. Although the offending cricket was banished from his room, he said that he could still hear the sound of the insect singing to attract a mate from outside.

Attack Still Possible

That, however, does not explain the health problems that the diplomats experienced after hearing the sounds. Albeit loud, the crickets are not responsible for the reports of nausea and headaches.

Doctors of the University of Pennsylvania ran tests on those who suffered ailments and found that the diplomats had concussion-like injuries. However, other medical professionals have cast doubts over the conclusion.

The researchers noted that while the audio recording obtained by the press were from crickets, it does not negate the possibility that the diplomats were subjected to an attack that made them feel ill.

"It's entirely possible that they got sick with some other completely unrelated thing that was not a sonic attack, or that they were targeted in some other way," added Alexander L. Stubbs of the University of California, Berkeley and co-author of the paper.