My 93 Accord started making a loud noise starting at about 55mph and by the time I hit 80mph, you couldn't even hear the radio over the noise.
The noise sounded like it was coming from the dashboard and sounded like a bad speedo cable, or at least one that needed lubricated.(the car doesn't have a speedo cable btw)

I finally decided to replace my speedometer assuming that the years inaccurate speedo was to blame for the noise even though it was not bouncing, just inaccurate.

After replacing just the speedo (not the whole dash cluster) the issue persisted.
At this point i figured that perhaps it was the electric motor on the odometer.
Rather then pulling the speedo cluster, I just disconnected the wires going to the cluster. This didn't fix the issue.

I then though, perhaps I left a bolt under the hood/wipers and it might just be rattling around. This didn't fix the issue.

It finally occurred to me what I had seen years ago on another vehicle. The weather stripping around the windshield had come loose (dried out) and it was flapping in the wind...