Can some one identify this sound coming from my engine? (1 Viewer)

[Larrythemoose]

Has anyone experienced this before?
It's an squealing sound coming from what appears to be the serpentine belt, it goes up and down with the rpms of the engine. What's odd to me is it doesn't happen all the time, I can start it up first thing in the morning and drive 20 mins to work and there's no sound but some mornings it does have the sound as soon as I start it up. Same thing happens when leaving work, sometimes it's there sometimes it's not.

Any help is appreciated.
Thank you.

Link to video:

 

[nissanh]

Simple, remove the belt and spin each pulley by hand and look for the same sound or faulty bearings. There are multiple bearings so check all. You would not believe my 21 Taco have FOUR idler bearings in addition to alternator, fan, water pump and AC.