Originally Posted by slvoid
That really depends on what type of helmet you wear (if at all) since the flow around that dictates the noise levels. It also depends on how your ears are shaped and where the wind is coming from. There's really no way to tell unless you take a head, stick a sound meter where the ear drum is, then measure it.
I just blew air over the sound level meter here with a piece of wax over it shaped like an ear and with a 25mph wind going over it, the SPL was averaging like 90dbA...
90 dB has an allowable exposure of just over 2 hours a day, assuming you don't work in a noisy environment, which is fine for 90% of commutes. The other thing to realise is that 25mph is pretty much unsustainable for most commutes, and even then, turning your head slightly to the side every minute or two (checking traffic or just looking at the...flowers) will reduce the noise to well below 90dB. I'd say that the worries associated with wind noise causing hearing loss are probably better expended on drivers being knobs or roads being crap. But hey, each to their own.