The sound is about 50 or so to ?? It is sometimes anoying, but the Metzlers also did this. It sounds like a basketball rolling down the road. You can hear a piece of rubber(tire, ball) over inflated(though its not) and making that sort of sound. Maybe I need louder pipes. Knowing that most of the tires do it, eg: truck tires, car tires, I don't wory about it. It is most likely from the front, because it became cupped after about 2k miles. They shouldn't have done that, but maybe they all do, I don't know. Seems like all my front tires on all of my bikes did.
I hope this helps, and by the way, I will always run these Dunlops, D251.
Good luck,
Kid