I recently gave AI's a paradox. When an ideal 10uF cap is charged to 100V, it has x charge, when an uncharged cap of 100uF is placed in parallel, the voltage goes to about 9.1V and the total energy is about 0.1x. If energy is neither destroyed nor created, where did the energy go? The AI kind of forgets that I specified an "ideal" capacitor, and makes shit up. If a human can explain this to me, I am all ears. Please keep in mind: "Ideal capacitor", and "equations show this", don't make shit up.
Consider the moment just before the two caps are connected to each other. One is charged to a nonzero voltage and the other is at zero. As the conductor attached to one capacitor top plate approaches the conductor attached to the other capacitor top plate (the bottom plates already sharing a common connection), the E field between them will at some point be high enough to exceed the breakdown field of the medium in between (even if it is free space). Then an arc occurs. That arc is observable, maybe even visibly. The "lost" energy radiates away as the electromagnetic energy associated with this arc.
The original article http://sandlab.cs.uchicago.edu... has some interesting graphs showing efficacy under certain situations. Looks like sometimes it can be fairly effective. What's missing are the frequency (ies) and sound energy the bracelet (transducers) puts out. Normal conversation is about 60 dB in amplitude. If you can get an SPL out of the transducers exceeding this, then the source (conversation) to noise (jamming) ratio will be low enough that the level will swamp the input of the listening device. The signal has to go through an A/D converter on the front end, and if you can get enough volume out of the jammer, that's all it will pick up. No amount of post filtering will make the signal intelligible.
Why is the mic picking up ultrasonics? In any case, to defeat this they could just put an analog low pass before the ADC. There should be one there already (the anti-aliasing filter for the ADC). Band-limiting the input to around 4kHz like POTS should do the trick. Not that I want this jammer to be defeated...
The moon is a planet just like the Earth, only it is even deader.