Welcome to the site. When does this happen? With engine running? Increase with engine rpm? While rolling? In park only or in R or D?
According to a thread I read on this forum the high pitch frequency is normal. Has something to do with ECU. Here what I found out. Need to worry less and drive more, is what one member said.
8. Q: Every time I turn off the engine I hear a soft, high-pitched whining sound from under the hood; it stops after about 30 seconds. Is this normal?
A: Yes. Opinions still differ regarding what's going on (the ECU is adjusting something in the engine), but we know that every '09 does it. My personal opinion is that this is your engine's way of saying "Weeeeeeeee! That was fun!" Its that kinda car. Update: a recent VW TSB ascribes this noise to the EGR valves: "After switching ignition off, the EGR system must go through an adaption of the valves to maintain calibration. These noises are considered normal...."