Diagnosing RPM related high pitch whine/noise

[notorious]

Hello all,

My D2 FL suddenly developed a high pitch whine, which can be clearly heard when I sit in the car while the car is parked.

Noise is clearly RPM related, but it is difficult to say where the noise comes from. Not even sure at this stage if it is from the front or from rear of the car. I appreciate there is nothing from rear that can generate RPM related noise, but simply judging by ears it is impossible to say where it comes from...

It is high pitch whine that kind of disappears with higher RPM perhaps because frequency goes so high that it becomes undetectable by human ear. Engine is revving a bit after 2000-3000 rpm, so it hides the noise too.

I tried to switch aircon on and off and play with steering wheel. Noise pattern does't change when I do that. It seem to be RPM related only.

* Is this bearing noise? No bearings in my car were changed yet.
* Can the RPM-related noise/whine be generated by smth other than bearing?
* In your experience which bearings fail first on D2? Any usual suspects?
* What are the best methods to isolate and diagnose problem?
* Any great tools I can buy that will help me to listen and isolate sources of noises/whines?

Any advice will be appreciated.