0·
4 days agoTo be a little more pedantic, they send ultrasound frequencies and they “degrade” into regular audible sound waves when they collide with something (combination of harmonic effects and destructive / constructive interference). The reason they send ultrasound instead of using regular directional speakers is because it’s smaller wavelength is easier to aim so much more of the energy moves forwards, so you don’t hear much noise coming from the source itself.
That’s why they work for “crowd control”. A strong enough regular speaker would bother the operator too much.
Federal law in USA is supposed to cover mostly commerce and interstate matters (and enforcement of constitutional rights) and what the states allow the federal government to manage. The federal gov is created as a contract between the states and a delegation of power from them.
So no. It’s kinda unusual in that way too, compared to other countries formed from multiple states.