Yeah, the 2006 models have been out for a while for most cars, and even mountain bikes.

 

Well, I have not noticed such noise so far in myA3...
That must be some kind of "Special Cause", I guess.

 

Its the turbo. The turbo does not spool unless under load. So in neutral with no noise I can almost say thats it. Mine turbo is very loud in the morning as well. I think ur okay. Check all ur lines and your air intake track too

 

Maybe the fan as the climate controll sensors kick in.

 

Try cleaning all around your side view mirrors. I had a previous car that did the same thing... as the speed of the wind passing through the dirty gap in the side view mirror, the whistle got louder... and all I needed to do was clean around the mirrors. If there is anything in there, and it's forming some type of hole for the wind to pass through, you'll get some serious whistling.