There is a certain amount of age-related high-frequency hearing loss, I think it's even got a technical medical name. A few companies have tried to capitalize on this making ringtones for cellphones at sufficiently high frequency that only people under ~30 should be able to hear it. The funny part is when students get in trouble when teachers who are in the small percent of the population that doesn't have this hear the phone ringing.

as per wind-noise. I figure a well sealed car's got to offer 20-30 decibels or so of attenuation, so most earplugs (just not the maximum strength ones) shouldn't be any worse than riding in a cage. they help for ignoring those silly cagers who wish to honk and yell at you too.