Hi Michael H,
Line the aluminum panels with self adhesive Dynamat. Will eliminate all harmonic vibrations of the panel. I lined my entire cockpit ( behind seats, side panels, floor ) with Dynamat. Made a big difference in noise reduction from vibrations. There are other sound deadening products out there besides Dynamat that probably would work as well.
Loose rivets will probably continue to rattle but the aluminum panels will be quiet.
How did the Dynamat project? Did you get a particular thickness? Difficult to install?
