At least 21 diplomats from the U.S. and more from Canada have been afflicted with what U.S. government officials have deemed “health attacks.”

These began as early as late 2016 and as recently as August, when word started to leak to the public. But what are these attacks?

Imagine you’re at home in bed sleeping and you wake to a loud clanging that’s blaring throughout the house, or you thought it was in the entire house until you jump out of bed and on the other side of your bedroom — and silence.

Or maybe you didn’t hear anything at all, you felt a vibration instead. But now you’re exhibiting the same symptoms as the person who heard the noise. Many reported concussions, permanent hearing loss, nausea, comprehension issues or brain damage.

Those are some of the narratives coming out from victims of these very mysterious “health attacks” from the homes and even hotel rooms where American and Canadian diplomats were staying in Cuba.

The initial thought was these were some kind of sonic attack — and that is exactly what you would think it is: Weaponized sound waves.

But the FBI, the CIA, the State Department, they say they’ve investigated this idea and have come up with nothing. They don’t know what would’ve caused these attacks, how they were carried out, who did this or even why.

To find out more, I went to a former senior adviser at the National Security Council Mark Feierstein. He's now at the Center for Strategic and International Studies.