The Subtle Pounding

I previously published a story called Eerie Things Started Happening to Me. Another thing that has been happening a lot since a few years ago is a subtle pounding. This happens about one night a month. In the silence of the night and only when I'm in the basement, I'll hear a subtle pounding that will go on anywhere from 10 minutes to 2 hours. I tried to ignore it, but it doesn't go away - it's not "in my head." Something is not "normal" about it, and pounding isn't a normal nightly noise. It sounds as if someone is very softly pounding the floor upstairs with his/her heal. It pounds about once every second.

A few times, in the pounding, I noticed what reminded me of the "human flaw," that is, it wasn't exactly equally spaced every second, but slightly staggered at some points - imperfect. The pounding also seems to slightly vary in forcefulness too, as subtle as it is. One night, in the midst of the subtle pounding, this one particular pound was harder than the rest causing the floor to "settle" (make a 'crack' noise). It also made the dishes in the sink rattle. Every time I go upstairs to find it, it stops, and then starts again only after I've been sitting downstairs for several minutes. I walked around my basement listening very closely and realized that it is in fact real, and it very much seems to be coming from my kitchen floor.

One night, after listening to this subtle pounding, I was in the kitchen almost ready for bed. I heard a loud thud on the kitchen floor as if someone in the basement hit the ceiling with a rock. It hit directly under where I was standing as I could feel the vibrations in my feet and legs. It was way louder than the normal "house settling."

Does anybody else have anything like this happen?