Squealing or grinding engine noise, Tiguan 2.0 TDI

Hello everyone,

Here are some details about my vehicle:

Tiguan 2.0 TDI - 4Motion DSG 7-speed DQ 300.
Year of construction: 04/2013.
65,000 km

Problem description:

I had a major inspection done at a VW service center. All the fluids were changed, and according to VW, everything is okay.
After that, I noticed that a strange "scraping" or "grinding" noise could be heard inside the car, especially when stopped (e.g., at a traffic light or in traffic).
I can hear it most clearly in the footwell on the driver's side.
The noise is speed-dependent, and I can hear it between idle and 2000 RPM. At higher speeds, it either disappears or becomes inaudible to me because the engine is too loud.
The lower the speed, the louder the noise.
It doesn't matter if the DSG is in P, N, or D.

You only hear it when you're sitting in the car. If you get out and stand in front of the running engine, you no longer hear this strange noise. However, this might be related to the fact that the TDI engine itself sounds quite rough. The noise is only audible when the engine is warm, after about 15-20 minutes of cold start, you hear nothing. The tachometer reading is constant; there are no fluctuations at idle.

What could that be?