Did you hear the noise before replacing the front brakes?
I got something similar when I replaced my front brakes with cross drilled slot rotors in the last couple weeks. I believe its the brake grease.
I redid them using synthetic brake grease. Its better. But not like with the old OEM rotors. I'll do it again. I think the added heat from aftermarket rotors are breaking down the grease on the sliders giving a similar noise to wheel bearing noise. I suspected initially in my case it was wheel bearings going but it was too coinidental to the timing of my rotor change. I brought the car in for wheel balancing and the guy checked the front end (i didnt ask him too) and he said it was solid.

Did you do the brakes yourself?

There is a hard way to find a bad bearings.

1. Jack-up the car
2. Rotate the tire one by one while holding the strut.
3. You can hear the grind and feel the vibration on the strut.

For the rear wheel, rely on your hearing.

check this out:

http://volvospeed.com/Repair/FWDbearingHub.htm
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Ken

When you hear the noise, did you try using your left foot on the brake lightly to see if the hum goes away? Don't forget to look at the ty rod bushings. If the bearing is starting to go to heaven, you should be able to feel play in the wheel by rocking the wheels by hand.

It's possible that your new pads aren't seated properly yet. A couple of 70 - 0 panic stops in a row will help with that.
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95 854T, 88 780, 88 245, 01 A4 Audi