This use to be a song i was trying to write. . . I failed miserably at the song but played around with some ambiance i created by accident and turned it into a piece or sound design instead. Good for a scene change in a horror film i suppose.
Selected snippet of http://www. Freesound. Org/people/theatomicbrain/sounds/238820/ with an immediate start, slow fade out, and pitch automation for a bit of a doppler effect.