Subtle World Explosions?

The other day a neighbor called me to ask me if I had heard the loud bang at around 4 am and all the dogs barking.  She wanted to make sure it had really happened and wasn’t just a dream.  She said that her husband felt the same way -that he wasn’t completely sure if it was a dream or if it had “really” happened.  Her teenage kids did not hear it.  I told that neither my wife nor I had heard anything that night.  “Hmm,” she said.  “Strange.”

It took me back to an experience I had back in college.  I distinctly remember being woken up at around 5 am by an enormous explosion.  I jumped out of bed thinking, “what in the world was that?!”  I later asked my friends if they had heard that large explosion.  They laughed and sarcastically said, “sure dude… we totally heard it.” 

Such a strange experience.  Has anybody else ever experienced something like that?  What do you think it could be?