We expected that our favorite, high-priced helmets would do a well on this test, and we were right. As a rule, the higher the price, the better padding and noise protection. The exceptions were AGV's Phantom and Thema, where price seems directly proportional to noise level. Shoei's X8, touted as the quietest, most aerodynamic helmet on the market, is quiet because it has more sound deadening padding in the comfort liner in this sized to fit very tightly. A Helmet that has less sound insulation will not necessarily allow you to hear more at highway speeds.
Earplugs effectively dampen wind noise, yet allow shrill sirens to be heard clearly.
However, if you drive in very slow traffic most of the time, where you need to notice external environmental sounds, a quiet helmet with thick padding may mask some of these essential sounds. These tests were performed without engine or external traffic noise, so they represent the minimum noise present at those speeds. Engine noise and external traffic noise add to the racket inside your helmet, though you'll notice it more at 30 mph than at 60 mph. Helmets like the Sure S8-N, AGV Sukhoi, Bieffe B3R, C. T. S., Fulmer, Hondaline, MDS, Nolan N35 and Jeb's all sounded louder than their rankings would suggest. None of these are fiberglass lids, suggesting that the type of material used in construction may play a part or that the cost of materials has an effect.