I moved to Colorado about 7 years ago. Since then I've had a lot of ear aches due to the altitude change. (I'm from Louisiana, pretty much sea level).. My ears would be ringing a little after the half hour drive to work... But about 8 months ago, I quit drinking caffeine for health reasons (cutting out all the caleries, the acids, etc in sodas). About a week after I stopped, my head stopped ringing when I drove..and now I can wear headphones for longer than 30 minutes without my ears feeling like they're going to start bleeding..
It's kinda weird what caffeine can do to you. I've probably drunk about 4 sodas since I quit (When I come into work exhausted and need the pick me up). If you have ear problems, you might want to try cutting back/quit drinking caffeine and see if it helps you.