Spaceships?

For the past two days, I've been hearing this crazy, deep, bass-like noise from somewhere or some neighborhood behind our house.  It didn't annoy me at first, probably because I didn't notice it.  When I began to notice it yesterday, I figured it would end soon.  It lasted all afternoon until about 5 pm.  

Strange morning, it's 11:16 am.  I woke up late this morning to Jehova's Witnesses at the door.  As I got out of the bed, I noticed the crazy noise from outside of the house.  "It sounds like an ..... orb," I said out loud.  That really is the best way that I can describe it.  It's such a low frequency, and it pulsates.  It's literally shaking the walls of my house and my head.  What IS that noise??  Then after the Jehova's Witnesses left, I turned on my mac to look some stuff up, and my power went out.  

The only logical explanation, is either a diesel engine is parked right behind my neighbor's house and won't stop the engine... or there is a new commercial building going up nearby.  

Make it stop.  

Have a nice day.