Strange sounds in the sky. Oregon

Script accompanying the video.
This is the 3rd morning in a row at roughly 3:00 am. The sound starts with a rumbling in the ground, and then the sound continues for roughly 30 minutes or so. Can not explain where it is coming from, it seems as if it is coming strait from the sky with not a single plane in sight. If anyone has anymore info. on this sound we are hearing, I would very much appreciate any explanation to what we are experiencing here in Oregon. Thank you.

This video was posted on my previous post by Elizabeth Prata of the End Time blog as a part of her post on the strange noise in the Oregon sky.
Jean-Louis