I noticed that when I put in a starburst FX while building my map, it created this really strange audio effect that loops. It sounds like a jet fly-by and never goes away.
I don't think it's part of the original map, unless somehow building on a platform put me closer to the sound of waves or something.
I wasn't too concerned with it, because fellow authors told me that it doesn't show up in the published versions. But, now that I've published, it is there.
So, it's either a bugged audio looping associated with the starburst or its something that the audio peeps should look at with the ground map. It doesn't sound organic. If I hadn't renamed the ground map, I could tell you what it is.