Ok, I only notice this when I'm going fairly fast, usually on the highway. I also only hear it when something is next to me and the sound can bounce back, such as a truck or jersey wall. But it sounds like a clicking noise happening at a very fast rate. I checked the tires for nails or rocks and found none. Any ideas?
Dan

 

Any ideas? Please?

 

Could be numerous things. A loose rocker or exhaust leak are a couple.