It is the short-range technology of beam-focused sound that makes secret the language of the mob.
Sound is a wave, diffused and without focus. Beam-forming sound allows for the placement of sound with near pinpoint accuracy, and the lack of familiarity of the police and the victim with the phenomenology of beam-forming sound gives the mobbers great advantages, setting the stage to meddle in the relationships of the victim and to run a hoax that the victim “hears voices” and has become crazy. Running this hoax successfully on a victim who is naive and fearful can end with the double-whammy of discrediting the victim reports and making the victim himself question his sanity and be panicked into leaving his home.
The primary tools for beam-focused sound are the parabolic loudspeaker and the parametric speaker. I suspect mobbers use both of them. The laser microphone is another beam-focused method of eavesdropping; I won’t cover that today.