The Ghost of Christmas Present

This is about the closest thing you'll get to a Christmassy post this year, I'm afraid, and I make no apologies for that. You know I'm not one for posting the same stuff everyone else is, so you might like this as a welcome-but-still-themed break from the more traditional festivities in blogland.

 I'm staying at my grandparents' house for a bit, and they've decorated for the festive season. One of their decorations is a string of red bells that hang between some of the photo hooks in their living room. During the day these bells hang still, but in the evening...

To clarify, those bells are 'ringing' all by themselves. They haven't been given a flick before hitting record: you'll notice that the oscillation does not slow down, and that ticking you can hear is the bell that's closest to the camera repeatedly hitting the glass of the photo frame. These collisions alone should do something to dampen the oscillations but as you can hear and see, they're continuing apace.

So what's the deal? I won't post it here because I think a few of you will like to get your noggins around this one. As a hint, there's a key piece of information that I've left out and isn't apparent from the video that goes some way to explaining this apparently supernatural phenomenon. Have a think, maybe ask some questions in the comments, and I'll post my assessment of things down there in a bit.