Any idea what this sound could be? CEL isn't on. Sounds like something is loose and knocking around but I have no idea what. It can be heard from inside the car. Any help I would appreciate.

 

Not completely sure but that almost sounds like a bearing of some sort. Just a shot in the dark but try taking the belts off of everything to rule out the ac compressor as well as alt. Farly certain that is not it, however you have to start somewhere and my personal sugestion is DO NOT DRIVE THE CAR!! Find that problem first

 

Most likely a rod as the others have said. Bottom end will need to be inspected and repaired or replaced.