Strange Sounds over Rapid City

At roughly 3pm on january 1st, 2012, my dog, milo began acting nervous and hiding under the table. Shortly afterward I heard a low rumbling sound, which I initially took to be an airplane until it didn't stop or fade out. I started listening to it, and thought that maybe it was my neighbors car stereo, but I could see that there was no one in their car, ad the more I listened the more obvious it became that it was not music. I went outside for a minute, and it was louder outside. I filmed the sound from inside my house because it is was 10 degrees F outside, and subzero with the wind chill. Also, quite frankly, I was scared out of my mind. You can hear the sound quite plainly, and it continued for what felt like about five minutes after I stopped recording.

I do live appx 20 miles from ellsworth AFB, where the testing of the B2 stealth bomber was mistaken for UFO's back when they were top secret, and I wonder if this is the same sort of thing happening? I do not know, but this experience has shaken me.