Gotta agree with Ninja here. It has the resonant sound that a plastic pulley makes when the spindle bearings go. You need to do some troubleshooting here. Pull off each belt one at a time and run the engine for a few seconds to determine which pulley is the culprit.
Of course, leave the timing belt intact. But you knew that anyways. If, after pulling the other belts, the sound is still there, then it is either the timing belt tensioner pulley, or the water pump. It it is either, then you might as well replace both, as well as the belt, since you will be in there anyways and will give you peace of mind for the next 60k miles.
Let us know what happens.
Mike (MKIII Emeritus)
Currently owned German vehicles:
2003 Volkswagen Passat GLX 2.8l
2003 BMW X5
2001 BMW R1200c (motorrad)
Previously owned German vehicles:
1996 VW Golf GL
1975 VW Microbus
1981 BMW 528i
1987, 1989, 1990, 1991 BMW 535i
1990 BMW 525i
1998 BMW 328i
1997 BMW 740il
"Non Sibi Sed Patriae"