humming noise in Cadillac
 

I own a 2003 Cadillac DeVille and it has, so far, been a good, almost trouble free car. Until recently.

I had new bearings installed on the front wheels, a new power steering line installed (it was leaking), and a new CV axle installed. I also bought new Michelin Symmetry tires. I had Toyo tires before these and it was after I had them rotated that I heard the humming noise. I thought it might be the tires and, since they had some wear, I decided to get new tires since I was taking a long trip out west.

The humming noise (not loud) sounds like it is coming from the front drivers side. My mechanic said he went over the car carefully and couldn't find anything. Since I intend to take the long trip west soon I don't feel comfortable driving that far until I know what is causing this noise.

Anyone have any comments as to what may be causing the noise?