It's not the first crowd control tool to use sound waves, but Raytheon's patent for a new type of riot shield that produces low frequency sound waves to disrupt the respiratory tract and hinder breathing, sounds a little scary.
Crowd control tools like the LRAD Sound Cannon emit bursts of loud and annoying sounds that can induce headaches and nausea. But Raytheon's non-lethal pressure shield creates a pulsed pressure wave that resonates the upper respiratory tract of a human, hindering breathing and eventually incapacitating the target. The patent points out that the sound waves being generated are actually not that powerful, so while protestors might collapse from a lack of oxygen reaching their brains, their eardrums won't be damaged in the process. Phew!