Hello dear memebrs🙂

I own Audi A6 (C7) 2.0 TDI Ultra S-Tronic from 2016. I hear whistling/whirling sound when accelerating slowly or harder from 60 mph/70 mph at 4th, 5th, 6th or 7th gear even if I drive slower and want to accelerate this sound is hearable from front of the car. The sound comes from left/centre/front side of the car and is noticeable behind the dashboard. When I switch gear on neutral when driving is quiet also if car is stationary on parking gear to do revving nothing is happening as well. The sounds appearing only when accelerating not when revving. Thank you