I didn't think much of this sound until my neighbor said it sounds like it might be an exhaust leak. What do you think?

 

Yeah, look for loose exhaust bolts or clamps. My exhaust system sometimes has a similar ding-ding sound. In the second half of the video it’s clearly a few valves that need adjustment.

 

I'd concur. Sounds like a manifold leak to me or possibly the collector. Crank it cold and run your hand around the back of the exhaust manifold. It's most likely back there towards the firewall. You might get away with just torquing the bolts again. Don't break 'em!