秦时鹿（Wuji Zhang）

There is noise (like a small stone hitting my window) on the window side of my room. The sound seems to be close to me (not from a distant). It happens a couple of times now and then in a day. Since I have just moved inside this new building, and no one lived there previously, I have no one to consult about this problem. I hope this is a window quality problem, but it still doesn't make sense to me why a window would make a sound when there is no wind no sand no bugs no human touching. Another thing: my electric boiling bottle has a switch-on button, which also makes some clip noise when no one is touching. Any scientific explanation to those phenomenons? I love ghost and mystery stories but doesn't mean I want to live with a ghost...