I'm in a 3-yr-old, 2-storey, 3200 sq ft house. 2 bath, 5 bedrooms/office upstairs. Hallway runs down most of middle of second floor. In Spring/Summer, when my wife and I are downstairs for several hours, or when we first get up in the morning, the wall in hallway makes huge noise, like a sharp cracking sound (i.e. not the more common subfloor "creaking" sound. Once we walk down the hallway, no more sounds, but returns as soon as nobody is walking around. Builder has been very helpful, although unless he's here in early morning or late evening, he hasn't been able to really hear the problem.
I don't think this is a load-bearing wall, even though it runs perpendiular to the attack joists. Builder has pulled carpeting and added screws to subfloor, and even doubled up the floor joists below the master bedroom (thinking, at that time that the problem was subfloor/joist movement). He also drove several wooden wedges under floor sill of the wall in question.
It appears to us to be a settling problem, with the wall acting as a large drum head, broadcasting movement between the floor and the wall or floor sill. We've had a building engineer look at this as well, but so far, no progress.
Could the wall be installed improperly, i.e. under too much pressure between the attic floor joists and the second floor? So that in Spring/Summer when the wood expands, the noise returns (this seems to definitely be related to temperature - we live in Boise, ID, were outside temps this past winter have been in the 20-40 range and now, with noise returning, moving up to 50-65. The key, I think, is that once we walk around the "settled" wall/floor, and as long as someone is walking around upstairs, the problem goes away. But once we go downstairs for awhile, it returns. Let me know what other info you need, but if anyone can solve this for us, we going to give you the key to Boise! Many thanks in advance for your suggestions.