I don't know what's wrong with our fridge, but at various times throughout the day it suddenly makes very loud cracking noises. Normally it will make a few slight popping noises, a few seconds apart, and then it will make a really loud cracking noise, and then it will stop. The noise sounds like it's coming from somewhere in the back, in between the fridge part and the freezer part. The only thing that I can figure out is that something in the fridge is turning on to melt the ice in the drain part of the freezer and the ice cracking makes the loud noise. I don't know how fridges work, though, and why it would only be two or three times per day and why the noise would be loud enough to wake me up at night. It's a fairly new fridge, too, so it's a little confusing and annoying.