This is the one I had in mind: https://spectrum.ieee.org/semiconductors/devices/finally-a-likely-explanation-for-the-sonic-weapon-used-at-the-us-embassy-in-cub

This is the one I had in mind: https://spectrum.ieee.org/semiconductors/devices/finally-a-likely-explanation-for-the-sonic-weapon-used-at-the-us-embassy-in-cuba https://spectrum.ieee.org/semiconductors/devices/finally-a-l...