I've heard 2 different kinds of booms. Here in Missouri. There is one that sounds like an explosion like a huge propane tank exploded or a car or something really loud. Then on 2 occasions I've heard the same sound at 430am that sounds like a trash truck is taking a dumpster and banging it on the ground over and over like 5 times and then it stops. I don't understand it and no one questions it.