[Bagelfast]

This buzzing, humming sound from the dash happens on and off at times.
It happens when the car is warm and only can be heard at idle when very quiet.

Ac off, radio off, all windows up at idle, I hear the humming sound from the dash, its pretty annoying.

I lightly rev, and the sound is directly tied to the revs/rpm, and at 1,000 rpm the humming sound shuts off and goes away!

2010 E90 335i N54 with 28k miles.

Anyone have any idea what it can be?
To be more clear on the sound, since I cant capture it on video.. Its on a on/off humming/buz.. BUZZ buzz BUZZ buzz.. And when I rev lightly it gets faster, and at 1k rpm it disappears.