(WASHINGTON) — It sounds sort of like a mass of crickets. But not quite. A high-pitched whine, but from what? It seems to undulate, even writhe. Listen closely: Some hear multiple, distinct tones colliding in a nails-on-the-chalkboard effect.

The Associated Press has obtained a recording of what some U.S. Embassy workers heard in Havana, part of the series of unnerving incidents later deemed to be deliberate attacks. The recording, released Thursday by the AP, is the first disseminated publicly of the many taken in Cuba of sounds that led investigators initially to suspect a sonic weapon.

The recordings from Havana have been sent for analysis to the U.S. Navy, which has advanced capabilities for analyzing acoustic signals, and to the intelligence services, the AP has learned. But the recordings have not significantly advanced U.S. knowledge about what is harming diplomats. Officials say the government still doesn’t know what is responsible for injuries to its personnel, but the U.S. has faulted Cuba for failing to protect American diplomats on its soil.

The Navy and the State Department did not respond to requests for comment on the recording. Cuba has denied involvement or knowledge of the attacks.

Not all Americans injured in Cuba heard sounds. Of those who did, it’s not clear they heard precisely the same thing.

Yet the AP has reviewed several recordings from Havana taken under different circumstances, and all have variations of the same high-pitched sound. Individuals who have heard the noise in Havana confirm the recordings are generally consistent with what they heard.


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inRead invented by Teads

“That’s the sound,” one of them said.

The recording being released by the AP has been digitally enhanced to increase volume and reduce background noise, but has not been otherwise altered.

The sound seemed to manifest in pulses of varying lengths — seven seconds, 12 seconds, two seconds — with some sustained periods of several minutes or more. Then there would be silence for a second, or 13 seconds, or four seconds, before the sound abruptly started again.

Whether there’s a direct relationship between the sound and the physical damage suffered by the victims is unclear. The U.S. says that in general, the attacks caused hearing, cognitive, visual,…