Police use both systems for crowd control and physical/ mental manipulation.
L-rad long range acoustic devices use low frequency that can travel long distances and penetrate the body and mind causing disruption of physical and mental processes and are also used to manipulate thoughts and deliver subliminal messeging.
S-rad short range acoustic devices do no penetrate and only affect those near by, can cause burning sensations on the skin. Good to deter people for close up action. Can also cause tinitus like symptoms.

Both along with voice to skull cas be replicated with relatively simple technologies and schematics found online or in books, by good and bad actors alike.