I think it's tire noise that the body work just amplifies. The fork opening acts as a megaphone, directing the tire noise right up into your helmet. The more aggressive the tread, the worse the noise. I notice it on my 16 model, even with Pilot Road 4 street tires. You can get the same "tire noise" from most bikes when the front tire is worn and cupped when you lean into a turn. I hear the "zzzzzzz" of the front tire cornering any bike when the front is worn.