2000 Pontiac Grand Prix Road noise as speed increases

I have an annoying noise (loud hum) which started about the same time as when I had new tires installed. I assumed it was the tires, but now after about 5,000 miles on them, the noise got a little louder and now the noise diminishes or goes away when I turn to the right, but not the left. Noise (hum) gets louder as I go faster and is the same over rough or smooth asphalt and concrete road surface, so I now know it's not the tires. I suspect it might be the bearings or cv joint, but have never had this problem and can't put my ear at the tire while driving. The car does not shake, shimmy, or vibrate and takes corners very well. Drove California Highway 1 around the curves overlooking the ocean cliffs with ease. Puzzled. Would donate, but unemployed right now, so hopefully someone has an answer.