Squealing belt noise

Hello,
Typically a faulty belt of idler pulley will make a squealing or squeaking noise.

Here is a helpful video of diagnosis the process:

https://youtu.be/AEUe6uKxTv8

I have attached few articles that walks you thru the serpentine belt operations and provides some very good insight:
https://www.2carpros.com/articles/car-squeaking-noise
https://www.2carpros.com/articles/how-a-serpentine-belt-works
https://www.2carpros.com/articles/replace-serpentine-belt
https://www.2carpros.com/articles/how-a-serpentine-belt-tensioner-works
https://www.2carpros.com/articles/serpentine-belt-tensioner-replacement

I have also attached the belt diagram.
Please let me know if you have any questions.
Thank you.