Strange wheel noise

On my RS6, I have been noticing a weird howling type sound in the left front of the vehicle, which sounds like it is around the left front wheel. It has been happening randomly over the past few months, and when it happens it is usually when I am in slow traffic and not moving more than 20 miles an hour. It seems to go away as soon as I apply light pressure on the brakes or if I turn the wheel back and forth. It seems not to be there if I am moving at normal speeds. My steering and brake fluid levels are fine. I have been doing some research with ideas of possible the wheel bearing or maybe something going on with the caliper as a cause. Anyone with a similar issues who could provide some insight.

Bearing typically growls at higher speeds, especially when applying load to it (turning right in your case).
So it appears your caliper is dragging maybe. Or something (a rock?) got stuck behind the dust shield.

You may want to pull the pads out and see if you see anything unusual with the pads surface. While there out you can compress the pistons one at a time and see if they all compress with approximately the same pressure.