2002 Volkswagen Passat Clattering, Rattling, Engine noise a

Hello, Thanks in advance for any information (even if I don't like the answer:)
My 2002 VW Passat suddenly developed an engine noise that seems to be coming from the front top center area of the engine. The noise is very noticeable at idle and somewhat difficult to describe, but I'll try. The noise is constant but seems to be 'random'; in other words does not correlate to any 1:1 (or other ratio) rotation. The noise seems to have slight metallic sound that could be described as a 'Clattering' or 'Rattling' along with what might be described as a lower pitched 'squeaking' or 'squealing'. The noise is not noticeable at highway speeds, and the car does not seem to be suffering from any decreased performance. Other details probably worth mention is that the Passat is a 3.0 4-Motion GLX, the total mileage is 95,000, and the 80,000 mile service is about. Gulp.15,000 miles overdue. Again, thanks for any help. Jeff