Replaced both pulleys and tensioner - sound is gone. Once I removed the pulleys and spun them in my hand it was obvious they were bad. FYI I am at 110k miles.

Thanks
Tom

Ordered, will change out and report back.

I have not - not sure if the previous owner did (assuming not). I was going to order:

Volvo Drive Belt Idler Pulley - 31216198 - Qty. 2
Volvo Automatic Belt Tensioner Assembly - 31216199 - Qty. 1 (Comes with Tension Holder In-Place)
Volvo Serpentine Belt - 8653617 - Qty. 1

So this is probably it ...

Most noticeable at idle - it can best be heard at about 17 seconds into the video, sorry for the poor video:

https://www.youtube.com/watch?v=C84nIczsX8w

Anyone have a similar noise? I tried looking on the forums/youtube but none were close to the sound I have. I was thinking starting cheap with ...