Strange whining noise

[LukeC]

My 2018 B9 has recently developed a strange whining noise , and myself and the garage can't quite distinguish where it's coming from. We've narrowed it down to the alternator area, and when they had it in for MOT yesterday, they did some tests, clearing the alternator, cam belt, and turbo (we knew the latter wasn't the issue anyway). There's no other symptoms other than the whine on acceleration and deceleration. 

It's definitely mechanical, as no lights or warnings are being thrown up on the dashboard. 

I would appreciate any suggestions you may be able to come up with.

[Multispacer]

My 2018 B9 has recently developed a strange whining noise , and myself and the garage can't quite distinguish where it's coming from. We've narrowed it down to the alternator area, and when they had it in for MOT yesterday, they did some tests, clearing the alternator, cam belt, and turbo (we knew the latter wasn't the issue anyway). There's no other symptoms other than the whine on acceleration and deceleration. 

It's definitely mechanical, as no lights or warnings are being thrown up on the dashboard. 

I would appreciate any suggestions you may be able to come up with.

When you say you knew it wasn't the turbo, how did you eliminate that? I'm asking as on my Berlingo i developed a whining noise and it turned out to be a slightly bent blade on the impeller of the turbo caused by some debris that had hit it. The bend in the blade was very slight and although slightly annoying [the whining under acceleration] it was not enough of a problem for me to fork out on a new turbo on a vehicle that was over ten years old at the time and was still working fine [with the whine] for a good few years until the vehicle got sold [I did inform the purchaser at the time who didn't seem bothered]

[evdama]

Cambelt or Aux belt tensioner pulley bearings,alternator bearings,waterpump bearings?

Access to any of thses beside the aux belt is a laborious task so unless you have a hefty labour invoice I would doubt they actually checked it thoroughly.
Gearbox could be another source if its occouring on the road

[LukeC]

The mechanic had discounted the turbo on the location where thee sound originated. I'm more convinced of a bearing within the alternator or something else that area. It's definitely originating low and left of the engine bay.

I'm not too concerned as there's no lights, warnings, or loss of power, I just like things running right.

[evdama]

The component is giving you fair warning that it is failing .
In time it will self destruct and cause damage to the parts around it..