NaMcO wrote on Apr 22^nd, 2012 at 9:31am:

What noise? Make sure the A/C packs are working, that's most probably the issue and unrelated to the VOR tracking...

I agree with Nuno. I did some extensive testing and the only thing that gave me a buzzing sound while tracking a VOR, or even just flying around, was the APU. Besides, I don't think you need to have the APU on while flying. I don't use it once I have started the engines.

Included as a part of the extensive testing, was shutting down both engines when at 11,000 feet, and when I started the APU for the engin restart, that was when I heard the buzzing sound.

Mark