That definitely sounds like a bearings on something rotating. Could be anything from belt relay rollers or alternator/ AC compressor / power steering pump etc .
On another note my 4.2TDI also has a variety of noises the loudest /most annoying seems like a whistling kind of sound coming from the rear centre vents. It is rpm related but not directly, more like on a delay. For example no noise in idle but as you raise rpm the noise comes on slowly and if you stop at traffic lights or roundabout and rpm drop to idle the noise still keeps coming for couple of seconds and slowly dissipates, switching AC off does not affect noise at all. I notice that AC compressor shaft is a bit wet with oil and UV dye.
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Currently 8less
2011 Q7 S Line 3.0TDI, 2016 Tesla Model S 90D
8 history:
2006 A8 Sport 4.2TDI quattro SOLD,
1997 S8, reached end of life with gearbox failure
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