curious. any chance the tail-gate vent area is blocked? That could cause a pressure differential, like blowing across the top of a bottle, leading to a flutter of sorts.

just a thought because I find I get a lot of header noise, etc. when I have gear blocking that vent area.

 

I solved the problem with a piece of foam insulation, grey to match the vehicle (style needs are always imperative!), wedged at the center of the soundbar.
If necessary, the two rubber buffers can be "silenced" using the little sticky things you put on the table/chair legs to avoid scraping on the floor ...

 

Sweet! I am going to try that for sure

 

I have the same flutter. Doesn't bother me. I just worry that the top will fly off if the wind is strong enough to break the areas around the bolts in the back.

 

i know i had this problem when one of my rubber spacers came off. these set in place at the from of the top just above the sound bar. i replaced it and never had the problem again