I have had similar experiences to most on this thread. I would hear noises coming from my walls.
I would normally hear them in late morning and then again late at night. I especially heard them
as the sun would heat up the south side of my house on a cold day. I could often cause the noises
to happen by slightly pushing on the inside (or outside) of my wall. It was easier for me to cause
the sounds in late morning or late at night. Once I got the walls to make the sound it was hard
to get it to happen again right after. I would push the walls every night before I went to bed (I know that's crazy).
In several areas of my wall, I removed the drywall to see if it was rodents or studs moving.
I had a very difficult time getting the anything to move from the plywood toward the inside of the house.
Then I moved to the exterior. I had EIFS (Dryvit, Sto, Cynergy, etc.) cladding. I removed some of
the cladding (I know this is odd, but I was desparate to find the cause of the sound). I found out
that I didn't have any Tyvek in between the styrofoam and the plywood (in my case OSB).
I was able to reproduce the sound by rubbing the styrofoam against the OSB. So then I was pretty sure
it was just the styrofoam against the wood making all the noise. I was not sure why my walls were
abnormally noisy. We would be laying in bed and hear popping noises like there was drive-by
shooting going on. I believe someone did a poor job installing the Dryvit or something. There were
fairly large gaps in between the styrofoam boards (about 1/8 inch, when there should be no gaps).
Also someone told me that mesh used was cheap. It was odd because I could get the noise to occur
pretty much anywhere around the house, although it happened the most where the sun would heat it up.
It was all about the thermal expansion and contraction of the Dryvit system causing movement and rubbing
of the styrofoam against the OSB. I could tell it was the whole system moving because the noise would
occur throughout the entire wall and not just one area. Sometimes you could hear it start to move
and then the rest of the system would move.
I ended up paying a bunch of money and replacing my Dryvit with cedar and brick. Since we removed the
Dryvit, the noises are completely gone. If you are experiencing similar sounds I would almost
guarantee that it is the expansion and contraction of your house cladding (whether it be Dryvit or
vinly siding or anything that spans the wall in large areas).
The good news is that it is a just an annoyance and your house isn't about to collapse (which I thought
that mine was ). The bad news is that it will probably not be easy to resolve.
My suggestion would be to replace the cladding like I did (that was a ton of money). The only other suggestion
is to somehow put in expansion joints in the cladding. I believe the smaller the sections of cladding the less
overall movement and therefore less noise. In Dryvit, you could make cuts and fill with
expansion joints. This is probably a really bad suggestion because it is just more places that water can get
behind the Dryvit and cause you worse problems (that is why I didn't do it).
Believe me, I wish I had a cheap solution to give you, because I would have used it myself.
Anyways, I hope this post helps people out because I googled this topic more than I have ever googled anything
in my life and I could not find any quality information on this. I just keep winding up on pages that told me
that I had squirrels or rodents in my walls. These noises were going to be the death of
me if I did not get to the bottom of it, so I hope the next person can use this information.