I have the exact thing (as best I can tell from your description). I first noticed it on the clover-leaf exits from interstate highways...as the I would have the car in a long right-handed turn, I would get occasional sounds from the right front which I first thought sounded like the tire rubbing (the sound similar to when a bicycle tire rubs against a fender...if you remember those on bikes)...or like you said the sound of when you run over those 'washboard' bumps on a highway.
The sound is occuring more often and tends to also be associated as the car bounces in the turn. I've waited to take it in to see what it's doing.
