Pop.ogg
  by Traveler (http://www.freesound.org/people/Traveler/sounds/16064/), License: CC Attribution 3.0

FurnaceStart.ogg, FurnaceStop.ogg, FurnaceLoop.ogg
  by tc630 (http://www.freesound.org/people/tc630/sounds/47835/), License: CC 0 (Public Domain)