What tire pressure are you using? It is too late for this tire, but running the max allowed on the sidewall seems to slow the wear that causes the noise (cupping) or eliminate it . The Harley "book pressure" seems to encourage cupping, especially if that figure is used as a maximum figure and the pressure decreases below that figure before the tire is pumped up again.
probably cupping on the tire. Run you hand over the tire and if scaling like a fish then cupped and that is the noise. You can continue to ride but best scenario is repalce tire. Keep an eye on tire pressure.
Cupping or scalloping is normal motorcycle tire wear, is your an aggressive rider, it will be worse. The noise he hears is more than likely just that and more pronounced because the crown in the road is to the left.