What does /x/ think of this guy? https://www.youtube.com/watch?v=2mlIHHeF7cg
According to him, we're being bombarded with I guess infrasonic/ultrasonic frequencies of speech, computer generated pulsed speech to be precise, that he has devised a way to record.
Afaik I hasn't revealed how he records them (I'm assuming he has to do some kind of (de/)modulation conversion to audio he records with (non-)normal recording device/microphone), and he hasn't revealed the method because he says then the non-military advertisers/corporations selling stuff would start taking benefit of it.
According to him, this technology is used both for surveilance and bombardment of ideas. In surveilance he provides example of him walking stairs, then (presumably) AI will count and ask/state "that was 15 steps(?)" which he claims to have recorded. This would mean the system works like radar, they probably pollute entire cities with signals that then bounce on people and stuff, and some device collects that back. The system can thus make observations of what any given people are doing, and we already know they record whatever you say with phones at least (has happened to all of us, get recommended stuff on facebook or youtube based on what you said to someone irl about some topic, sometimes a random obscure youtube channel with 2k subscribers gets in your front page).