Being surrounded by smart devices, it is only necessary that some of us are concerned about how much these devices get to see, here and sense. And who gets access to that data - in other words, who gets to see what we do and hear what we say.
This concern is highly unfounded. Even if you believe misuse by the vendor is not a concern, you may still worry that your smart device may be "hacked" by a third party harboring some sort of a nefarious intent. And so being able to make those smart devices if not dumb, then at least deaf certainly has a value to it.
And now a portable solution may be at hand. A research team at the University of Chicago has designed a bracelet emitting ultrasonic pulses that garble audio input at a microphone thus rendering "bugs" or local smart devices practically useless. There apparently are commercial outfits already planning production of such devices, to be offered for sale at about 20 USD.
Notably, like any other powerful technology, this one comes with some pitfalls. One could potentially use it to suppress microphones used to provide transparency - for example, at political speeches, in interrogation rooms at police stations, etc. But what this invention definitely accomplishes is drive home a universal point that for most, if not all technologies, there is an antidote technology.
Ultrasonic bracelet jams the microphones around you
Jon Fingas, Engadget, 15 February 2020