Not a Barn Owl? They sound as if someone is being murdered. Maybe your search can be narrowed by visiting: allaboutbirds.org Enter in your area, and a list of possibilities may appear. Good luck.

Perhaps it's the sound of a screech owl!

Every night in owosso Michigan, their is a screeching noise that doesn't match any owl sound.i researched it for An hour and found nothing. It almost sounds airy.and it's very high pitched, and kind of long. It can be heard only in trees.