Dogs have very sensitive ears. They can. hear frequencies beyond our range. I remember my mother joking that the dog would sometimes make her nervous, as his ears would prick up when she had heard nothing, Dog whistles are whistles which operate at a frequency humans cannot normally hear.
Source: Baha Men https://www.youtube.com/channel/UCRfuo4-sVlWEhA7QqDjHn8Q
People use dog whistles on each other too. Key words and phrases are repeated so frequently that targeted individuals become highly attuned to them whilst individuals who have not been sensitised remain blissfully unaware. The effect of uttering these words or phrases becomes automatic. They can seem to induce an almost trance~like state in the target.
I am not particularly knowledgeable about Hitler’s speeches but feel sure that they wold have been full of dog whistles ~ phrases which would, after constant repetition, have had an almost hypnotic effect upon the German people. Th use of dog whistles is something which is still in widespread use today.
Source: BBC News https://www.youtube.com/c/BBCNews