I have seen paranoid dogs too.
I think you guys are right about the fears reflecting the culture the people live in.

In the mythology there seems to be a common thread of warning, it does not seem to matter if they say those voices are fairies, leprechauns, mermaids, Rhiannon or the Windigo.
Almost every culture tells their people not to follow the voices they hear into the woods (or onto the rocks for sailors)

The fact that the stories are all similar says that it is a common thing and that indicates it is something normal brains do. Kind of an auditory instead of a visual mirage.

I find it very interesting that cultures where people often spent time with no sound of a human voice around regarded this as normal and developed myths to explain and warn about it.

That tells me it is something to beware of if you are ever in deep isolation.
I know with a visual mirage there is a difference in the quality of the image, and that you can usually tell a mirage from reality once you have seen them.
So how would you tell auditory mirage from real sounds?
I suspect you might have more difficulty locating it, and the sounds might be just a bit to perfect in tone. I am not sure but I really do suspect there would be some traits of the sounds that might help you decide.

Some studies have been done on prisoners in solitary confinement. They showed very strong signs of audio hallucinations, and mostly of the terrifying sort.