Strange Noise at Specific RPM's

[GoldenEagleFan]

It's been cold as hell here in Wisconsin and the last few days I've had this strange noise at specific rpm's. The noise sounds like a guitar sounds when you get feedback through the amp. Very distinct at very small range of RPM and fades out below and above this ROM. It occurs at approximately 3,600 rpm in 3rd gear, 2,900 rpm in fourth, and 2300 rpm in fifth. I though maybe it was some wierd ice formation creating a noise or the cold air having just the right denisty to have a hemholtz effect with some feature on the exterior etc, but when I use the speed function in the OBC the RPM's correspond to slightly different speeds. 87 Km/hr in 5th, 89 in fourth and 92 in 3rd.

Right now it's just slightly bothersome but I am curious if this is a sign of worse things to come. Any idea?

[RallyD]

on another car I had a loose exhaust heat shield would cause a funky tone at very specific conditions on my commute to work. It was funny because I knew when it was going to happen and would anticipate it.