Name that noise. 99' Porsche 996 engine noise?
 

I was finally able to figure out how to post a UTube recording of the engine noise.

The noise only appears after driving about 3-4 miles. Not on startup and not noticed it warming up in garage.

Once the sound appears it doesn't go away even at idle. Seems slightly linked to RPM's (increase/decrease) but not like a direct noise-rpm relationship.

A couple guys listening thought it might be a loose sparkplug or a pully issue. Need expert opinion.

https://www.youtube.com/watch?v=Qle3bhfNizA

Sounds like a bearing to me, pulley or alternator perhaps?

Thanks for your suggestion. I had a couple of suggestions as to what it was. I didn't want to just start throwing replacement parts at it and I was worried it might be a deeper issue (valves? Piston slap?)

I took it to a mechanic today and he seems to think is bearing noise from a belt fan pulley as you suggested. We are going to put a new one in and see if it solves the problem.