Most of us are familiar with the optical phenomenon known as a mirage. Such illusions are triggered by certain combinations of the auditory stimuli of frequencies and rhythmic patterns, with perhaps varying pitch. Auditory illusions are not uncommon. There is a branch of psychology known as Psychoacoustics which studies auditory perception, including auditory illusions.
Human speech is a combination of frequencies and rhythms.
All of these sonic events can, and do, exist in forms outside of human speech. It is not unlikely that each of us at some time in our life will mistake a sound such as the creak of a door, or the scrape of a chair across a floor, for a human utterance. This is an auditory illusion. It is of course possible to misinterpret auditory stimuli in ways unrelated to speech through precisely the same mechanisms. The examples involving speech are just a special case.