I would be interested in the reaction of those investigators, and vice versa, as to how this could in fact be done physically in the place where this allegedly happened. And how the effect was accomplished through numerous normal physical barriers and then affected some while not affecting others.
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 2017
We created a proof of concept eavesdropping device to
exfiltrate information by AM modulation over an inaudible ultrasonic carrier. When a second
inaudible ultrasonic source interfered with the primary inaudible ultrasonic source, intermodu-
lation distortion created audible byproducts that share spectral characteristics with audio from
the 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 to
cause harm could have led to the audible sensations in Cuba.
I found out that the Peace GUI EqAPO has a MeierCrossfeed functionality.
the problem doesn't show up.
I will do some testing to try and reproduce it consistently
so we will have some more clues, hopefully.
i guess i will concentrate on a classic car radio with support for flac & high sdcard capacities then. this seems way more practical than a smartphone in combination.
concerning the lack of gapless playback, it is indeed a plague, especially when listening to (seamless) audiobooks.
thinking about what is important for me when looking for a new classic car radio:
+ should not be too expensive (under 100euros)
+ vorbis or opus codec support (incl tags)
+ good handling (intuitive way of selecting files/folders) / nice arrangment of buttons (skip, seek, mute)
+ clean interface / screen (no fancy blinking stuff, option to turn off ->> light on resources)
would be nice to have: gapless playback
well, that's it i think