Odd High Pitched Noise

[lsand]

Car is a 2003 9-5 2.3L turbo, auto trans, 49,500 miles.

Today I started to get a high pitched warning tone type sound that appears to be coming from under the center of the dash. The noise only occurs while driving and it stops immediately when the brakes are applied. Noise occurs whether AC is on or not.

First thought was perhaps brake warning pad sensor, checked the brakes plenty of pad left.

Any thoughts would be greatly appreciated.