I wanted to post this before I left on the cruise but didn't find the time.
While packing for my cruise I kept hearing this periodic sounds. It sounded sorta of like moaning but not too loud. I thought maybe one of my neighbors was having a good time :). I noticed that it got louder while I was in the bedroom. I tracked down the sound. You might need to turn the sound up on the video below for the full effect.
It's not the first time I've caught Jobu snoring. He woke me up one night.