The Daily Parker

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What really was the Cuban sonic weapon?

About a year ago, a number of American diplomats and their families in Cuba were injured by what our military speculated might be a sonic weapon. A sonic weapon directs sonic energy at a target to disable, but not necessarily permanently damage, the person. Over a few months, people reported "blaring, grinding noise," hearing loss, speech problems, nausea, disequilibrium...exactly what a sonic weapon could cause.

Via Bruce Schneier, a team at the University of Michigan working in association with the IEEE has published a paper speculating on the variety of weapon how it might have worked:

On the face of it, it seems impossible. For one thing, ultrasonic frequencies—20 kilohertz or higher—are inaudible to humans, and yet the sounds heard by the diplomats were obviously audible. What’s more, those frequencies don’t propagate well through air and aren’t known to cause direct harm to people except under rarefied conditions. Acoustic experts dismissed the idea that ultrasound could be at fault.

Then, about six months ago, an editor from The Conversation sent us a link to a video from the Associated Press, reportedly recorded in Cuba during one of the attacks.

To make the problem tractable, we began by assuming that the source of the audible sounds in Cuba was indeed ultrasonic. Reviewing the OSHA guidance, Fu theorized that the sound came from the audible subharmonics of inaudible ultrasound. In contrast to harmonics, which are produced at integer multiples of a sound’s fundamental frequency, subharmonics are produced at integer divisors (or submultiples) of the fundamental frequency, such as 1/2 or 1/3. For instance, the second subharmonic of an ultrasonic 20-kHz tone is a clearly audible 10 kHz. Subharmonics didn’t quite explain the AP video, though: In the video, the spectral plot indicates tones evenly spaced every 180 Hz, whereas subharmonics would have appeared at progressively smaller fractions of the original frequency. Such a plot would not have the constant 180-Hz spacing.

Of course, to this day, no one knows exactly why the attacks occurred, and even to say "attacks" makes a reasonable but not certain assumption.

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