The phenomenon of hearing intelligible voices or noises in meaningless background noise is known as “auditory pareidolia.” The sources of this noise vary; they may include electric fans; running water; airplane engines; the hums of washing machines; or white-noise machines, according to audiologists. It is an auditory sub-type of pareidolia, in which people see faces or other meaningful patterns in ambiguous images.
This happens to me all the time surveying through tall corn. I have to stop every few steps and listen to make sure one of my crew members isn’t lost or something, only to realize it’s just the wind rustling the corn.