I've got a few q's for you--or just a good picture of the tread from teh tires will work

what speed does begin and end at? and what speeds does it produce noise?
do your wheels require hubcentric rings?
Have you had your suspension checked recently?
How often do you rotate your tires?
when was the last time you hit a pothole at a decent speed? and was that tire up front when you hit the pothole?
when you had your wheels balanced did they mention anything about cupping or seperation or flatspots?
when you run your hand over the tread, do you feel any highpoints or ridges, and does it occur in any sort of a pattern?