'Sonic Attack' On US Diplomats In Cuba Sounded Like Shrieking Crickets

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HAVANA (CBSMiami) – A recording of what some U.S. embassy workers heard in Havana, believed to be the cause of their serious injuries, has been released.

The recording was obtained by the Associated Press, and is part of the investigation into who was behind the mysterious attacks.

It sounds similar to shrieking crickets but with an electronic twang.

"Americans who heard these sounds in Havana have described slightly different sounds. And even in some of the recordings that the AP has reviewed there are slight variations. However, this high-pitched crickets sound seems to appear in all of them," said Josh Lederman with the AP.

The recording is just one of the many sounds taken in Cuba that led investigators to initially believe it was a sonic weapon.

An analysis of the sound reveals there are roughly 20 distinct tones within the sound.

The AP said 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.

But more than a year later, still no answers.

"We still don't know what is causing the sound and the recordings don't appear to have significantly furthered the investigation. Even with the recordings being analyzed, the U.S. government still says it has been unable to determine what is causing the sound," Lederman said.

The U.S. says in general the attacks caused hearing, cognitive, visual, balance, sleep and other problems.

"It's possible that what we're hearing on the recording is actually only part of the picture. Traditional recording devices are only able to pick up certain types of frequencies such as the ones that the human ear can hear," Lederman said. "It's possible there are additional frequencies possibly those too low or too high to be picked up that are also happening when these attacks occur."

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

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

So if it is the Cubans, what's the motive? There is a change of leadership coming as Raul Castro steps down early next year.

"There is a strong possibility there are people in the government, Hank, that might not want the relationship between the U.S. and Cuba to get any friendlier from the fear that they could lose some political control within the ranks as that position goes from Raul to Miguel Diaz Canal," said Cuba expert Andy Gomez.

Cuba has denied involvement or knowledge of the attacks.