It's not overly loud. I just don't hear other loud vehicles without the radio off and the windows open, and I don't typically have the radio off and the windows open. This has always been the case for me in any vehicle at highway speeds.

I suppose it could be the opposite. A very quiet car. What make, model, and year? I’ve been looking for a quiet car. BMWs seem really quiet on the inside. My friend bought one because he wanted to shield his child from freeway homier when they were driving.

I have a 2000 Oldsmobile Intrigue and a 1999 Chevrolet Silverado 1500. They are not quiet on the inside. Lots of air leaks and stuff. I just don't understand how people hear other loud vehicles going 70MPH or so. I have good hearing (according to my latest hearing test) and unless the loud vehicle is extremely loud (like big truck with a jake brake) then I've never hear the neighboring vehicles in any vehicle, not just the two I currently have.

Edit: If I'm able to hear them, it's immediately after they have passed me.