Walking sounds at the Cotton Exchange

I work down at the Cotton Exchange in one of the upstairs offices.  We have between 10 to 16 people working there day and night.  I'm on the night shift.  We have something, ghost or something that walks back and forth my row of cubicals'.  The floors are wooden had make a very recognizable sound when walked on.

You can hear footsteps starting at one end of the passage way, about 15 feet, then the door at the end opens, very slowly, stays open for a second and then slams shut, very loud.  I would love to see if anyone else has see or heard anything