My belt tensioner squeaked and rattled...>>> Clicky
Had it replaced...squeak and rattle gone.
But, I would check your belt out a little further.
Make sure you don't see any cracks on the underside in the ribs.
You can also narrow down the noise by doing the following:
Grab a long flat blade screwdriver.
Place the blade end on an accessory of your choice, and the handle end in your ear.
It will transmit the sounds, and you might be able to find the culprit.
BE CAREFUL around moving components!!!
A vacuum hose will also work, and is a little more versatile in tight spaces,
though it doesn't transmit the sound as well as the solid screwdriver would.