A whine or screech that rises with boost. Bearings or the wheel itself.
Worn turbo bearings, shaft play, or a damaged compressor wheel eating its housing.
Ease off the boost and get it inspected. A grenaded turbo feeds metal to the engine.
Reading about sounds only goes so far. The tuner on our home page listens in your browser and tells you what it hears. The app goes further: it names the exact fault, checks it against your vehicle, and tells you how urgent it is.