Could my house be haunted?

After living in the here for 17 years, I'm beginning to wonder if my house is haunted.  Or maybe it's just my office.

Sometimes I get up earlier than my husband.  (Okay, I ALWAYS get up earlier than him.)  And I'll be sitting here in the office and it's deadly quiet.  And then the noises start.  Things bumping around.  It'll sound like someone is taking the pool tools (which hang on the side of the house) off and putting them back up again.  Every so often there's a really loud CRACK that seems to come from around the window that overlooks the (postage-sized) back yard.

I've given it a LOT of thought and ... I'm pretty sure that I'm afraid of ghosts.  Can they harm you?  I don't know.  Do they want to communicate?  Maybe that's why all the noises?  We have a farm behind us--no people--so don't have drapes on that side of the house.  But sometimes I get nervous and wish we did.  When the noises start, will there be a ghostie hovering outside my window or just a plain old burglar?  (Burglars usually don't want to be caught so are QUIET. So who's making all this noise?)

I used to babysit for a couple who had a noisy house.  "Don't worry, the house is just settling," the lady would say every time they left me in charge of their kids.  Well, it sure settled a lot when I was there.  There were all kinds of bumps and noises.  I did not like babysitting for them and was glad when I finally just stopped babysitting altogether.

So where do you think all these noises in my office are coming from?