It could definitely be pulley related. Pull the belt and run the engine to see if it goes away. While the belt's off, free spin the pullies. If they free wheel and rattle, there's your problem. A proper one should be silent and spin with some resistance then come to a stop.
I did all pullies and tensioners along with Continental belts and it's nice and quiet up front now. No more chirps or bearing rattles.
I have a new INA drive belt tensioner pulley if you want it. It's OEM. $10, I'm in Winston Salem.