You need to target some specific location in the brain for that, if that is even possible in humans.
Ultrasound is not very conductive by air [1]. The frequency used in the research process is 3.2MHz, and we can safely conclude it will be absorbed much (looks like thousands times) faster than sound in human voice range.
The power needed to control the crowd with this technique will be prohibitively big. You can just use boat sirens with 1/100 of the power and get same crowd-dissipation results.
Ultrasound is not very conductive by air [1]. The frequency used in the research process is 3.2MHz, and we can safely conclude it will be absorbed much (looks like thousands times) faster than sound in human voice range.
[1] https://www.researchgate.net/figure/Attenuation-of-sound-in-...
The power needed to control the crowd with this technique will be prohibitively big. You can just use boat sirens with 1/100 of the power and get same crowd-dissipation results.