Front end whine while driving

My vehicle has recently started to have a whine, or humming sound while driving down the road. It sort of sounds like the noise a big lug tire makes on asphalt. Or some 4x4's make with the hubs locked in. The pitch of the sound changes as speed increases, but does not change when the transmission changes gears, so I do not think it is in the transmission.

Occasionally I feel a vibration when I turn at slow speeds, maybe from the differential?

There is no excessive noise when up to highway speeds, it is more noticeable from about 15 - 45 mph.

There is no cupping or uneven tire wear.