Rattle Noise coming from front passenger side

Hello, I'm hoping someone will hear this sound and know exactly where it's coming from on my 2009 Armada. I can't tell if it's a pulley or the tensioner maybe? It's the same no matter what RPM and no matter what load. It's not constant or steady, but really annoying. It's most obvious from about 36 seconds on, in this video:

https://www.youtube.com/watch?v=8xQtnac6RPM

Thanks for any help. :)

Charlie