1. They cannot claim they discovered constructive/destructive intereference
2. They cannot claim they discovered interference that shifts frequency.
3. They cannot claim to have "Reverse engineered the Cuban "Sonic Weapon" attack"
They instead PROPOSE the U.S. Embassy in Cuba has brain-altering levels of noise in the ultrasonic region somehow caused by two or more simple,low level and possibly common ultrasonic emitters without malicious intent and THAT'S why some people can hear it...
Xu's other recent works has been lacking meat and are better at fear-mongering (Tesla ultrasonic 'hack', Smart grid 'hack').
Xu's ultrasonic Tesla 'hack' showed how dangerous the pedestrian avoidance system was by wrapping one of her graduate students in Michelin Man-sized ultrasonic dampening material. Tesla had to make an uncharacteristically brusque comment stating they couldn't reproduce anything of risk to Tesla drivers in the world.
She is the equivalent of the National Enquirer in the security research world and steadily increased her ability to clickbait.
Couldn't they obtain a 7khz tone by mixing any two tones seperated by 7khz and applying a low-pass filter? I don't see how this proves anything.
And the 155dB number cited by the Canadian government would require considerable (hundreds of watts) of power to produce at close range.
This whole case defies logic. The early reports were of mysterious symptoms not associated with any obvious exposure. Once ultrasound/infrasound began being mentioned, people began reporting hearing mysterious sounds.
The recording makes even less sense: If the sound levels were really sufficient to cause physical trauma, surely they would overwhelm the phone's microphone?
A low-pass filter would filter everything out assuming the threshold is below the two frequency. The beat frequency of the two tones would indeed by 7kHz, but if you think of the resulting waveform, the contingent parts are smaller, faster oscillations that that would be suppressed by the filter.
> Couldn't they obtain a 7khz tone by mixing any two tones seperated by 7khz and applying a low-pass filter?
I don't understand this comment. Are you implying that a low-pass filter would shift the frequencies of part of the signal rather than (mostly) filtering some of the frequencies away...?
> In the most common application, two signals at frequencies f1 and f2 are mixed, creating two new signals, one at the sum f1 + f2 of the two frequencies, and the other at the difference f1 − f2.
Then the low pass filter is used to remove the original signals and the sum, leaving only the difference.
When they are mixed they produce a beat frequency. When it is sampled at a lower frequency only the beat frequency remains.
I may be wrong but I think a filter would have the same effect in this case.
My point is that any number of inputs could produce the observation, so their claim of reverse engineering is rather questionable. In fact they have no evidence of ultrasound at all.
The other attack they described ("DolphinAttack") is intriguing. I've yet to read the paper (but plan to), but the idea of Voice control being ever more present and likely extending to control of more parts of our lives (Banking, Vehicle Controls, Home Security...) could make this a pretty effective attack vector.
What a weird, rambling article. I read the whole thing and I'm really not sure what point they were trying to make. Two ultrasonic signals can interfere to produce lower wavelength sound? That's kind of obvious to anyone who has studied signals...
A) We have recording from Cuba, therefore there's proof of ultrasonic noise.
B) This noise we have is in the audible spectrum, but we have reason to suspect it's from the interaction of two ultrasonic frequencies that together produce a very whiney audible frequency
C) Ultrasonic noise can be used for spying and voice-injection, so there's a potential motive for the US to use such technology at an embassy.
Just a brief question from a non-engineer: Is this the same kind of phenomenon that produces the illusion of a fifth voice in a barber shop quartet? Thanks!
> Xu’s 2017 paper “DolphinAttack: Inaudible Voice Commands” describes how we used ultrasonic signals to inject inaudible voice commands into speech recognition systems such as Siri, Google Now, Samsung S Voice, Huawei HiVoice, Cortana, Alexa, and the navigation system of an Audi automobile.
So cool. I had this idea a long time ago but never approached it. Kudos to them for some follow through.
Until and unless they actually test their "reverse-engineered" device with live subjects under similar conditions to what has been reported in Cuba, how valid is that claim?
Edit: this is, of course, a rhetorical question. The "reverse-engineered weapon" claim is clearly false.
They make this point themselves in the article: they can account for the unusual recording from Cuba, but not for people's symptoms.
>> While the math leads us to believe that intermodulation distortion is a likely culprit in the Cuban case, we haven’t ruled out other null hypotheses that may account for the discomfort that diplomats felt. For example, maybe the tones people heard didn’t cause their symptoms but were just another symptom, a clue to the real cause.
> While the math leads us to believe that intermodulation distortion is a likely culprit in the Cuban case, we haven’t ruled out other null hypotheses that may account for the discomfort that diplomats felt. For example, maybe the tones people heard didn’t cause their symptoms but were just another symptom, a clue to the real cause.
Unless what I read was just plain lies, I don't see how this is plausible. Just reading The Guardian's article [1] I see no room for other plausible explanations in every case... remember there were at least 21 US victims (!!):
The blaring, grinding noise jolted the American diplomat from his bed in a Havana hotel. He moved just a few feet, and there was silence. He climbed back into bed. Inexplicably, the agonizing sound hit him again. It was as if he’d walked through some invisible wall cutting straight through his room.
Soon came the hearing loss, and the speech problems, symptoms both similar and altogether different from others among at least 21 US victims in an astonishing international mystery still unfolding in Cuba. The top US diplomat has called them “health attacks”.
New details learned by the Associated Press indicate at least some of the incidents were confined to specific rooms or even parts of rooms with laser-like specificity, baffling US officials who say the facts and the physics don’t add up.
Note that the purpose of the microwaves doesn't have to be frying someone's brain or creating sound; it can be some unrelated attempt to e.g. try to intercept data think about possible attempts to use preexisting materials in a way similar to https://en.wikipedia.org/wiki/The_Thing_(listening_device)
Constructive interference of microwaves is the most likely candidate I think. Each beam would be essentially harmless, but at their intersection you’d have a bad time. This could be used by adversaries to power bugs as you reference in another post, but also by friendlies sweeping for bugs. As a bonus the emitters could be compact compared to some monstrous speaker systems, and probably mobile.
When the title and the bulk of the article imply that they actually did reverse engineer whatever hurt the diplomats, a few weasel words don't make TFA true, they make it clickbait.
What? The weasel words at the end are good science, not weasel words. They're explicit about what they have and haven't determined.
They've done impressive work figuring out why the "ultrasonic" attack would have an audible component. They can now reproduce the tones heard in Cuba using an ultrasonic source, something that didn't make sense before. Responsibly, they never claim that the "ultrasonic attack" is conclusively responsible for the actual harm, although it appears likely.
The "ultrasonic attack" really deserves a few dozen scare quotes at this point, people with experience of using ultrasound on humans deem it unlikely to actually cause harm in any covert way, and I do trust the medical profession to find pretty robust limits on how dangerous ultrasonic devices are.
So given that there is no convincing reason to believe ultrasound has anything to do with it, they've now demonstrated a way to make audible noise as a consequence of interaction between two ultrasonic sources. They chose this particular (obscure) way of getting audible sound from an ultrasound emitter because a journalist sent a video of a sound whose relevance is that it was recorded on Cuba.
And the great result is that now you need at least two ultrasound emitters, one of which is a bulky 155 dB emitter just lying around undetected in the homes of American diplomats. I don't see how the explanation of a minor problem with the ultrasound theory is any great advance.
I remember reading about audible sound produced from interference of ultrasound decades ago. As TFA indicates it's just math, which math has certainly been done before now. After reading TFA, I'm not convinced there was an attack, that if an attack occurred it had anything to do with ultrasound, or that if an ultrasound attack occurred it had any of the qualities discussed in TFA. It's interesting to compare this credulous hypothesizing with the article by the same author in the sidebar that is super-skeptical about the pacemaker hacks, which hacks have since been confirmed by FDA.
It seems like the ultrasonic emissions were more likely a byproduct of whatever caused the physical symptoms, though the article makes a hand-wavey reference to people getting ill from such emissions.
I was also looking for the results of a human experiment. Math is great and all, but if there's no human symptoms that mimic the original reports, this thesis is just a science experiment.
How can they really know they "reverse engineered" the "weapon" unless they have sync with actual human symptoms. It's not the study (or university policies) I take issue with, it's the way they present their study as conclusive. It's not conclusive.
Note: the HN title has been changed from the original "How We Reverse Engineered the Cuban “Sonic Weapon” Attack" which is the actual title of that IEEE Spectrum article.
You don't need to burn someone alive to know that putting someone under certain heat conditions is going to kill them. Similarly, you don't need to actually expose people to crazy powerful sonic waves to know that they would suffer from it; just knowing that the waves were there and inferring how to generate them is enough.
All of this is obvious though; you aren't being rational about this, like you have a dog in the race.
2. They cannot claim they discovered interference that shifts frequency.
3. They cannot claim to have "Reverse engineered the Cuban "Sonic Weapon" attack"
They instead PROPOSE the U.S. Embassy in Cuba has brain-altering levels of noise in the ultrasonic region somehow caused by two or more simple,low level and possibly common ultrasonic emitters without malicious intent and THAT'S why some people can hear it...
Xu's other recent works has been lacking meat and are better at fear-mongering (Tesla ultrasonic 'hack', Smart grid 'hack').
Xu's ultrasonic Tesla 'hack' showed how dangerous the pedestrian avoidance system was by wrapping one of her graduate students in Michelin Man-sized ultrasonic dampening material. Tesla had to make an uncharacteristically brusque comment stating they couldn't reproduce anything of risk to Tesla drivers in the world.
She is the equivalent of the National Enquirer in the security research world and steadily increased her ability to clickbait.