Spirits?

As I was sitting at my sewing machine yesterday, working on a bag order and fooling with my computer at the same time (I can roll my chair back and forth easily), I heard my bedroom door rattle softly. I got up and opened the door, thinking a cat or dog was accidentally shut in the room. Nothing there. Went back to sewing. Rattling again. I thought it was the other door which is right next to the first door. Nothing there either. I looked all around. Matt was napping on the sofa and wasn't stirring, although later he would say he heard it too. This happened around half a dozen times. I didn't feel scared, or weird, no hairs standing up on the back of my neck, etc. It wasn't until later that I thought, wait a minute. We are not close enough to the highway for trucks to rattle doors. The doors are far below the hay mow floor and wouldn't be shook by cats running above. There are no windows open. I just couldn't think of a reason for the doors to rattle - maybe a supernatural reason? I know this farm is haunted...maybe a spirit is saying hello?