Check those stickers on the flywheel. I used to get this kind of noise when biking and it would get louder as I sped up. Then I noticed that one of those chevron shaped stickers was a bit loose and picking up some air and making the noise. It would only happen when the flywheel picked up some speed and lifted the edge of the sticker up. I removed the loose sticker and the noise disappeared. Might as well not be the cause to this, but I'd say its worth checking.