Definitely scary shit.
There are methods that can be used to alleviate the effects of audible offensive weapons, from placards used in protests to some solid shielding otherwise (makeshift riot shield), but for inaudible subsonic weapons, I only have theories based on the way RF works. In short, aluminum foil *should *work to protect from inaudible weapons like shown in the video. If the shield were to be made concave and faced towards its origin, it could end up focusing it back to where it came from as well. “Space blankets” should act as a shield as well without reflecting it back (instead dispersing it).
If this is a variant or evolution of ADS tech, you may be exactly backwards, OP.
https://en.m.wikipedia.org/wiki/Active_Denial_System
Basically, its a microwave beam, that can be aimed broadly to make a crowd disperse by heating the top layer of their skin.
Some redditors are saying it may have been this.
If it is/was that, aluminum foil or space blankeys would heat up considerably more rapidly than exposed skin, and likely cause significant burns.
However, a redditor in that thread posted this:
https://youtube.com/watch?v=y0pYU1qNEQE
And this makes it seem more like it is a kind of directed sound weapon… which would be this:
https://en.m.wikipedia.org/wiki/Long-range_acoustic_device
If it is/was that… you’d have to have a phalanx of concave shields to attempt to scatter the sound, but the problem is that it is such high db that the sound would just bounce around off the ground and buildings… and you’d also have to know exactly where it was coming from, and somehow coordinate a whole crowd to do an aimed testudo formation… and account for 3 dimensions, not just two.
We’re talking up to 160db, louder than being right next to a jet engine or rocket launch.
Your best bet would be basically gun range or flight deck or heavy industrial grade ear pro.
Both of these kinds of tech are usually mounted on cars or trucks… but nowadays, drone versions also exist.