Oh, by all means, I'm not expecting to capture anything. I've just never had the chance to try and document a supposed "paranormal" phenomenon before, so it might be worth a shot (who knows, could be worth a million bucks!). If I'd only capture the audio, that would be interesting enough.
I'm way too skeptical to believe that there's something paranormal creating the sounds in the stairs, but I have to say that I did experience this before I was told all the rumours from the people I work with that the place is supposedly haunted, so I wasn't exactly expecting it. But I agree, in general it seems like a lot of "believers" tend to over-interpret everything in favour of what they believe in (as do the skeptics, though, truth be told). There are lots of sounds there at night, but most of them I've been able to discern (like you say, pipes, doors, the wind, windows, creaks in the wood etc), but the staircase sound really is intriguing - as it sounded exactly like it does when someone is walking down those stairs, footsteps and the reverberation of those footsteps inside the room.