Hum when slightly turning at all speeds.

[kitsrider]

While driving the X5 2003 3.0 at all speeds I get a slight hum whether I turn right or left. It is much louder on the highway. At first I thought it was coming from the rear but (checked sub frame and rear control arm bushings, and no play) definitely coming from the front. While driving at highway speeds, nice and quiet while straight, minor movement of steering wheel left/right creates hum or throbbing sound, no shimmy of vibration. Don't really know where to start.
Wheel Bearing?
Thrust/Control arm bushings?

Anyone experience these symptoms?
Thanks