IEEE Spectrum - Reverse Engineering the "Cuban Sonic Attacks" 2018-03-18 17:57:52 Starting in 2016, various (mostly American and Canadian) diplomatic personnel have reported bizarre health effects, with symptoms so strange they were often not believed, and which are potentially even linked brain abnormalities in affected personnel. The Cuban government has (I'd suggest plausibly) denied any responsibility for the strange "attacks", and there seems to be no immediately obvious medical explanation for the symptoms.In the official IEEE publication Spectrum, two enterprising US & Chinese professors and a grad student have put up a fascinating article providing a plausible explanation for the combination of audible noise and (potentially) detrimental health effects that might be linked to exposure to high powered ultrasonic devices, and most saliently, why ultrasonic devices would be used in a diplomatic context (to quash and/or engage in eavesdropping). In essence, their explanation boils down to Intermodulation Distortion causing the audible effects. Their Spectrum article is essentially distilling bits of their research paper manuscript (pdf direct link), (much of) the abstract of which I'll quote below:Quote from: Yan, Fu & Xu 2017We created a proof of concept eavesdropping device toexfiltrate information by AM modulation over an inaudible ultrasonic carrier. When a secondinaudible ultrasonic source interfered with the primary inaudible ultrasonic source, intermodu-lation distortion created audible byproducts that share spectral characteristics with audio fromthe AP news. Our conclusion is that if ultrasound played a role in harming diplomats in Cuba,then a plausible cause is intermodulation distortion between ultrasonic signals that unintention-ally synthesize audible tones. In other words, acoustic interference without malicious intent tocause harm could have led to the audible sensations in Cuba.Fascinating Stuff!