Hey,
Watching a random episode of the American television show "Hoarders" I heard a sound that I knew very well. Now it may just be a public domain clip that Bjorn Lynne used when creating this music, but listen below and see what you think.

The hoarders clip can be seen here (http://www.aetv.com/hoarders/video/#10778179678) if you fast forward the video to 2:40

The same sound can be heard in several places in the WA song "Cavern" here (http://www.youtube.com/watch?v=MC_EF7j4g-Q) if you fast forward to a spot like 2:59

Yeah, most of the sound effects are public domain, but some of the sounds Bjorn recorded himself in his garden.
You can read more about that here: http://wa.team17.com/main.html?page=abou&area=thet&inte=bjor