an acoustics expert and engineering professor at The George Washington University who reviewed the recording with the AP.
Those frequencies might be only part of the picture. Conventional recording devices and tools to measure sound may not pick up very high or low frequencies, such as those above or below what the human ear can hear. Investigators have explored whether infrasound or ultrasound might be at play in the Havana attacks.
The recordings have been played for workers at the U.S. Embassy to teach them what to listen for, said several individuals with knowledge of the situation in Havana. Some embassy employees have also been given recording devices to turn on if they hear the sounds. The individuals weren’t authorized to discuss the situation publicly and demanded anonymity.
Cuban officials wouldn’t say whethertheu.s.hassharedtherecordings with Cuba’s government.
Another big question remains: Even if you know you’re under attack, what do you do? Still dumbfounded by what’s causing this, the United States has been at a loss to offer advice.
The embassy’s security officials have told staff if they believe they’re being attacked, they should get up and move to a different location, because the attack is unlikely to be able to follow them, the commenting individuals said. The AP reported last month that some people experienced attacks or heard sounds that were narrowly confined to a room or parts of a room.
At least 22 Americans are “medically confirmed” to be affected, the State Department says, adding that the number could grow. The attacks started last year and are considered “ongoing,” with an incident reported as recently as late August.
Cuba has defended its “exhaustive and priority” response, emphasizing its eagerness to assist the U.S. investigation. Cuban officials did not respond to requests for comment for this story but have complained in the past that Washington refuses to share information they say they need to fully investigate, such as medical records, technical data and timely notification of attacks.
The recordings also appear to rule out one possibility for a high-tech weapon: Electromagnetic pulses.
The broad array of symptoms reported, including those not easily explained by sound waves, had led to questions of a possible microwave or radio wave device frying body tissue from afar. Research conducted by the U.S. military decades ago showed that short, intense “pulses” of microwaves could affect tissue in the head in a way that was interpreted by the ear as sound, meaning that a microwave device could potentially “beam” sounds directly into people’s heads.
If that were the case, the sounds wouldn’t show up on a recording.