[bmgxyz]

I think this is a neat idea, but I suspect it would be more useful as a standalone device than as a wearable. Devices like this could be installed in secure rooms or deployed on the fly in discreet locations with a high rate of success, I'd guess. Arrays of them could work together for better coverage.

Still, this may be the only real option in public spaces (i.e. outdoors). If you're okay with people knowing that you're trying to avoid being recorded, then this would probably be fine.

[moftz]

They make it a wearable to counteract the nulls caused by the multiple speakers. Random movement causes the nulls to not stay in one place for very long, limiting how much of a word or sentence a microphone could pickup. You could build a phased array of these that could quickly move a hotspot of ultrasonic noise all over the room. You could them position on the ceiling with a fixed radius between them to make sure that the highest pressure occurs at about waist level, where phones in pockets, smart watches on wrists, and smart speakers on tables would reside. Another idea would be a ball of these in the center of the room and have it move up and down to get the best average coverage around the room.

Smart assistants are usually not recording really high quality audio, it takes more time to process it and more time to send it back home so they are going to a lower sample rate than typical voice recorder app would use. Siri uses a 16KHz sample rate (Fs=16KHz) which is enough to put the whole human vocal range in the 1st Nyquist zone (less than Fs/2). Playing a sound at 26KHz (3rd Nyquist zone, >Fs but <1.5*Fs) is going to cause a reflection across Fs. So the 26KHz tone, sampled at 16KHz, creates a tone at 10KHz which could be enough to confuse a naive implementation of a smart assistant. Ideally, you want fix this by either installing an analog filter so the ultrasonic noise can never reach the ADC or sample the whole range (up to 44.1KHz is a good start) and filter digitally.

There is a paper called DolphinAttack [1] where they attempted to use the ultrasonic audio band as an inaudible attack vector. You could play an ultrasonic noise that no one can hear except for the smart assistant.

[1] https://gangw.cs.illinois.edu/class/cs598/papers/ccs17-hidde...

[stubish]

This only defends against off-the-shelf mikes, and adversaries will just get better mikes so not particularly useful in the security space.

It is illegal public and most commercial spaces as most organizations need to follow anti-discriminatory legislation. Spaces unusable by people with hearing aids, hearing dogs or just very good hearing is not going to happen.

[Defenestresque]

They mention that the wearable component was a conscious design choice to overcome certain limitations of standalone devices:

(On standalone device limitations)

>(2) They rely on multiple transducers that enlarge their jamming coverage but introduce blind spots locations were the signals from two or more transducers cancel each other out. If a microphone is placed in any of these locations it will not be jammed, rendering the whole jammer obsolete.

>To tackle these shortcomings, we engineered a wearable jammer that is worn as a bracelet, which is depicted in Figure 1. By turning an ultrasonic jammer into a bracelet, our device leverages natural hand gestures that occur while speaking, gesturing or moving around to blur out the aforementioned blind spots.

[tsumnia]

I envision a variation that sits in the corner of a room, similar to how a fan operates, gradually turning the speakers. However, as others mentioned, I'm curious over the effect it would have on hearing aids, etc. Secondly, if there a variation of this device that could straight up disable WiFi?

[BeefySwain]

Jamming wifi (as well as many (most?) other frequency bands) is very simple and very illegal.

https://en.wikipedia.org/wiki/Radio_jamming

[tsumnia]

Right, that'd be my concern - that if their implementation could be modified in a similar manner to create jammers that would be quick to deploy but difficult to locate.

[moftz]

You could just have a simple Wifi deauth beacon. You can do it with a simple ESP8266 and could either kick everything off the network or target blacklisted MAC address ranges. It's usually illegal to do this to someone else's network just like running a real Wifi RF jammer.