Thanks for the info and welcome to the forum jsj041277! I am going to have to bring it in and see what they think.

 

I have an 06 too, 63,000 miles....same sound like its from back axle...rev it slowly without music in the car youll hear it clearly.

 

Just started noticing this a month ago on my 2017 Discovery, approx 35k miles and 1 month out of warranty, go figure!. Exact circumstance as luxury1 indicated. At idle a noticeable high-pitched hum that doesn't change with RPMs. Fan off, radio off. Once I begin to move (at about 12 mph) the sound "switches off". I distinctive on/off. Back on when I stop. Noticeably loader standing in front of the engine bay but can't pinpoint where it is coming from. Off to the dealer to find out!