DanieldH Posted February 27, 2020 Report Posted February 27, 2020 Watch out for those 🕵️♀️ http://sandlab.cs.uchicago.edu/jammer/ The video seems broken, the German tech news site Golem has it. https://video.golem.de/audio-video/24095/wearable-microphone-jammer.html However, the video is less interesting than the question, how this works... and on what mics. Quote
borjam Posted February 28, 2020 Report Posted February 28, 2020 At high sound pressure levels ultrasounds can produce audible sounds when colliding with objects. The transition between different mediums (air and a solid body) creates a non linear effect. For example, it is possible to beam an AM modulated towards a wall. The beam will be demodulated and the modulating signal will be heard like it originated from a spot on the wall. https://en.wikipedia.org/wiki/Sound_from_ultrasound I have seen it working, a friend was experimenting with this some time ago. I guess it will provoke a similar phenomenon on the microphone diaphragm. Quote
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