My girlfriend’s 2005 Saturn Relay minivan has an intermittent buzzing at speeds around 75 mph that sounds like it is coming from the passenger side of the dashboard. She thinks it is due to the radio antenna being loose. I think it is something inside the dashboard, but feeling around while the buzzing occurs doesn’t help isolate it. It tends to occur more when she drives. She doesn’t use cruise control and drives 75-79 mph and the buzzing drones on. I set the cruise on 73-74 and rarely hear it. Any ideas are welcome and would greatly reduce unpleasant trips. 
Slow down a little. What’s the rush?
Not a big deal…what, 3-5 mph slower to avoid a noise that will likely be next to impossible to find.
Plus you might save gas too.
Radio antennas can make noise,why not remove the mast (if possible and see?)
Have you ever looked at a late 90’s (and later) GM mast? there is what looks like a thick thread that spirals down the mast,I am told it reduces noise.
I wonder if this noise could be comming from the windshield rubber gasket (this was common on early Malibu’s,not the real early ones.)
The buzzing now occurs as low as ~60 mph, so slowing down isn’t an option or we’ll getting ticketed for impeding traffic. I read a TSB for Malibus about a similar buzzing, and the fix is applying double-sided tape between the plastic cowl and the windshield. I might try that.
Also, I isolated another rattle to the airbag door on the passenger side. Has anyone had similar rattles and how did they fix them? It’s amazing how many rattles these vans have.
That is the overspeed warning. A lot of Saturn owners think this is a problem, but it is an unadvertised feature.
Thanks for the tip, and it sounds about right.