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Researchers Provide Likely Explanation For the 'Sonic Weapon' Used At the US Embassy In Cuba (ieee.org)
An anonymous reader quotes a report from IEEE Spectrum: Last August, reports emerged that U.S. and Canadian diplomats in Cuba had suffered a host of mysterious ailments. Speculation soon arose that a high-frequency sonic weapon was to blame. Acoustics experts, however, were quick to point out the unlikeliness of such an attack. Among other things, ultrasonic frequencies -- from 20 to 200 kilohertz -- don't propagate well in air and don't cause the ear pain, headache, dizziness, and other symptoms reported in Cuba. Also, some victims recalled hearing high-pitched sounds, whereas ultrasound is inaudible to humans. The mystery deepened in October, when the Associated Press (AP) released a 6-second audio clip, reportedly a recording of what U.S. embassy staff heard. The chirping tones, centered around 7 kHz, were indeed audible, but they didn't suggest any kind of weapon. Looking at a spectral plot of the clip on YouTube, Kevin Fu, a computer scientist at the University of Michigan, noted some unusual ripples. He thought he might know what they meant.
Fu's lab specializes in analyzing the cybersecurity of devices connected to the Internet of Things, such as sensors, pacemakers, RFIDs, and autonomous vehicles. To Fu, the ripples in the spectral readout suggested some kind of interference. He discussed the AP clip with his frequent collaborator, Wenyuan Xu, a professor at Zhejiang University, in Hangzhou, China, and her Ph.D. student Chen Yan. Yan and Xu started with a fast Fourier transform of the AP audio, which revealed the signal's exact frequencies and amplitudes. Then, through a series of simulations, Yan showed that an effect known as intermodulation distortion could have produced the AP sound. Intermodulation distortion occurs when two signals having different frequencies combine to produce synthetic signals at the difference, sum, or multiples of the original frequencies. Having reverse engineered the AP audio, Fu, Xu, and Yan then considered what combination of things might have caused the sound at the U.S. embassy in Cuba. "If ultrasound is to blame, then a likely cause was two ultrasonic signals that accidentally interfered with each other, creating an audible side effect," Fu says. "Maybe there was also an ultrasonic jammer in the room and an ultrasonic transmitter," he suggests. "Each device might have been placed there by a different party, completely unaware of the other."
Fu's lab specializes in analyzing the cybersecurity of devices connected to the Internet of Things, such as sensors, pacemakers, RFIDs, and autonomous vehicles. To Fu, the ripples in the spectral readout suggested some kind of interference. He discussed the AP clip with his frequent collaborator, Wenyuan Xu, a professor at Zhejiang University, in Hangzhou, China, and her Ph.D. student Chen Yan. Yan and Xu started with a fast Fourier transform of the AP audio, which revealed the signal's exact frequencies and amplitudes. Then, through a series of simulations, Yan showed that an effect known as intermodulation distortion could have produced the AP sound. Intermodulation distortion occurs when two signals having different frequencies combine to produce synthetic signals at the difference, sum, or multiples of the original frequencies. Having reverse engineered the AP audio, Fu, Xu, and Yan then considered what combination of things might have caused the sound at the U.S. embassy in Cuba. "If ultrasound is to blame, then a likely cause was two ultrasonic signals that accidentally interfered with each other, creating an audible side effect," Fu says. "Maybe there was also an ultrasonic jammer in the room and an ultrasonic transmitter," he suggests. "Each device might have been placed there by a different party, completely unaware of the other."
Who would be using the transmitter? Who would be using a jammer. Moreover, which nation-state/s would bother with using ultrasonic in an age of cheap RF based technologies?
Life is not for the lazy.
They looked for stuff like that, and didn't find it. Unless they are wholly incompetent, that's not the problem.
"You're right," Fisheye says. "I should have set it on 'whip' or 'chop.'"
Why would an IMD product be more harmful than any other audio signal of normal intensity and spectral content? That question needs to be answered before this theory can be taken seriously.
Standing waves. I've been spending the last three years working in this space with audio processing, before I even open the paper I said to myself "I bet intermodulating waveforms" is a factor and there it was on the second page. I will most certainly read this whole paper however I thought I'd share some of my experiences that were a by-product of what I was trying to understand.
Out of curiosity I tried the experiment on myself and a few friends and found that if you hit the right frequency with a person, they will practically hit the roof and run away if they have any form of Tinnitus. I did a spectral analysis of the waveform and the best I can describe it is like audio teeth, waveforms with a specific Q, amplitude and frequency separation. I could'nt see anyone handling more than a few seconds of it, I have no doubt you would be very sick in much less than a minute.
If there were two devices they would cancel AND reinforce certain audio spectrum within the human hearing range thus you would get a combination of modulating and standing waveforms would be *really* disorientating, anything more than 5watts at that frequency range would be nasty. Just moving around in the room would make it oscillate.
It's not just humans and please don't hold this against me, I love dogs too, but not when they bark until 5am and sleep all day while I am driving down a freeway fatigued. Complaining to neighbors doesn't work but an intermodulating waveform oscillating between 23k and 25k works in under 10 seconds. No neighborly confrontation required.
The last thing I found is that it doesn't have to be actual damage to your hearing to produce the effect. I have my hearing tested often, I know exactly where the damage is and the effect is not necessarily related to damage.
A final point though is wind turbines. I think the effect is the same however it is intermodulating infrasound with very long waveforms relating to the characteristics of the turbine blades in different turbines interacting with each other. I would not live near these devices any more than living next to a main road, it will slowly make you sick.
Obviously my pithy experiments aren't controlled so I'm interested in what this paper has to say, maybe it can answer some questions I have.
My ism, it's full of beliefs.
Back in my days working on secret stuff, meeting room windows were equipped with piezoelectric transducers used to defeat laser inferometer microphones. It's possible that our embassy was so equipped. This would explain one ultrasonic source. Possibly even multiple sources in rooms with lots of windows and poorly installed systems.
Have gnu, will travel.