Buzzing sound

The wife's '06 has developed a buzzing sound at the base of the windshield near the center. It starts at approx 60MPH so I assume it's air going over/thru something and causing the buzzing. I've checked/cleaned the area under the hood thinking it was a leaf causing the sound. Can't see anything that could be making this sound. Anyone else ever have this problem?

Figured it out!
There is a thin piece of plastic which goes around the edge of the windshield. The edge would vibrate when the airspeed/direction was correct. Different sections would vibrate at different times causing the sound to "move" at times. Kept putting clear packing tape on various spots until I found this. Will fill this area with clear sealant after I remove the tape.