The U.S. Embassy in Cuba
The U.S. Embassy in Cuba U.S. Department of State

Over the past months, a strange story has been unfolding: Diplomats working in Cuba reported that they had been experiencing severe hearing loss and mild head trauma. According to the U.S. government, those symptoms were caused by a sonic attack, perpetrated by unknown parties, in which some sort of device was used to sicken the U.S. personnel.

This is, to say the least, a very strange and unusual story. What in the world is going on? Here’s what we know.

The Timeline

The State Department first heard about the attacks in late 2016; they started within days of the presidential election. The initial reports included what the Associated Press called “unexplained losses of hearing.” Among the first people affected were U.S. intelligence agents. In March 2017, Canada’s Foreign Affairs Department heard reports of similar symptoms—“headaches, nosebleeds, dizziness, ringing in the ears,” The Star reports.

The AP reports that the U.S. government started an investigation into these strange incidents and concluded that the embassy workers’ hearing loss could have been caused by “an advanced device that operated outside the range of audible sound and had been deployed either inside or outside their residences.” Investigators also found, according to The Guardian, that the attacks were concentrated in three clusters, at the homes of U.S. diplomats and at hotels they frequented.

Americans working for the embassy in Cuba had started to come home for treatment or chose to leave their postings. In May, the U.S. State Department responded by asking two accredited diplomats at the Embassy of Cuba in the U.S. to leave the country.

In August, the story of the “sonic incidents,” as the State Department was calling them, became public. At the time, a spokesperson stressed that there was still no definitive answer about what was causing these symptoms. In the same month, another round of incidents was reported. By late September the State Department was considering closing the embassy, and Secretary of State Rex Tillerson met with the Cuban ambassador. Soon after, the U.S. removed most of its employees from Havana and suspended visas for Cubans. Early in October, the U.S. had 15 more Cuban diplomats leave America.

A view of Havana from a hotel popular with Americans.
A view of Havana from a hotel popular with Americans. U.S. Department of State

The Sounds and Symptoms

In total, there have been 22 confirmed cases of people being hurt by these sonic attacks. As reporting on the incidents increased, so did the list of symptoms the diplomats had experienced, which included “mild traumatic brain injury and permanent hearing loss, but also loss of balance, severe headaches, cognitive disruption and brain swelling,” according to ABCNews.

Although the original reports said the device operated outside the range of audible sound, by mid-September the AP was reporting that victims had heard sounds, including a “loud ringing or a high-pitch chirping similar to crickets or cicadas,” a “grinding noise,” or “a ringing in their ears.” The AP also found that “some of the incidents were confined to specific rooms or even parts of rooms with laser-like specificity,” adding to the puzzle of what was responsible. The Associated Press obtained a recording of what the victims were hearing; you can listen to it here. (It is very annoying.) The sound is not dangerous to listen to on your computer, but the victims said they heard it a much higher volume.

To date, no actual device linked to these attacks has been found.

The embassy had only recently reopened, in 2015.
The embassy had only recently reopened, in 2015. U.S. Department of State

The Science

What type of “advanced device” could cause these sorts of symptoms? To cause hearing loss, a sound needs to assault the ear’s delicate mechanism until it’s overstimulated and stops working. If the sounds were inaudible, they would be either in low-frequency or high-frequency sound bands. A high-frequency sound can be directed in a tight beam, which would stack up with some reports that the sound was incredibly localized—just stepping a few feet away could mean escape. But high-frequency sounds cannot travel far, and a device that generated enough to cause damage would likely be pretty large.

The Alternate Theories

In the earliest public reports, the State Department floated the possibility that a third country (possibly Russia) was behind the attacks. Since then, the list of potentially responsible parties has grown to include Iran or rogue Cuban military officials.

There have also been many theories floated about what else might be causing these symptoms. Wired set out a case that the same symptoms could be caused by chemicals that caused hearing loss and that had somehow been weaponized to use against the diplomatic community. The New York Times suggested that a bacterial or viral infection could also have been the cause.

It could also be the case that the reported attacks are a case of mass hysteria. Because the symptoms reported are somewhat vague, several scientists have told reporters, they may actually be the result of anxiety and psychological pressures, rather than any mysterious device.