17 Expedition XLT engine rattling noise

[Mooncaller]

Sounds like the serpentine belt. It sounds normal to me.

You gotta use headphones to hear it clearly.
Thing is that rattling noise comes and goes, I figured it's not from the ventilation system.
I just can't figure out exactly what it is.

 

[MidnightBruce]

Sounds like cam phaser knocking. What is your oil change interval? Mine makes a similar sound.