Looking for suggestions here. I recently purchased a new Shoei Multitech helmet. I ride with the face shield up. I have a Tulsa standard height windshield on the bike and I'm 6'2" tall. When riding at speeds over about 40 mph, I get a fairly loud low frequency rumbling sound coming from the helmet. It goes away when I close the face shield. It's worse with the top air vent open, but still there, and annoying with the vent closed. If I place my hand, vertically on top of the windshield, the noise pretty much disappears. I suspect that a taller windshield is the (most expensive) cure, but I'm wondering if any of you who have a Shoei Multitech helmet experience the same thing and if there is anything that can be done. And please don't suggest I buy another, different helmet. Thanks.