I use earplugs about 90 per cent of the time and always when I'm travelling on highways or going above city speeds.
Use Laser Lite, made by Howard Leight. Cost me 15 cents per pair at a local safety equipment store. Buy them by the dozens and ony wear them for one or two days max.
http://www.survivair.com/Products/Ho...site=/americas
Huge reduction in noise and I feel far more comfortable on the bike. Well worth the minimal investment.