What would cause a strange noise in a car, above 30 mph that sounds like a combination rattle and buzz?

Driving back from some Christmas shopping and the right, front side of the car started making a strange sound. It was a combination sound. Almost like a calf blatting. I couldn’t find anything loose or out of shape. It started at 34 mph and stopped below that. The handling or performance didn’t change a bit. It got louder at higher speed. Then it went away. Any ideas?