The answer was blowing in the wind.

[crg]

We're down on the south coast for a holiday and there was a weird buzzing noise like something loose was flapping at speeds over 80km an hour. There was nothing obvious to see, and nothing hanging out the doors, but it was definitely a new sound.
I pulled over at a rest area and got down on my hands and knees and found the side skirt on the driver side was buckled, loose and not attached properly. Having banged that back into place the noise seems to have disappeared. Not sure how it got loose - there are no signs of damage. Anyone else experienced this?

 

[nhcowboy28]

We're down on the south coast for a holiday and there was a weird buzzing noise like something loose was flapping at speeds over 80km an hour. There was nothing obvious to see, and nothing hanging out the doors, but it was definitely a new sound.
I pulled over at a rest area and got down on my hands and knees and found the side skirt on the driver side was buckled, loose and not attached properly. Having banged that back into place the noise seems to have disappeared. Not sure how it got loose - there are no signs of damage. Anyone else experienced this?

A few of mine were loose after I took delivery.

 

[crg]

The door sills are quite wide. I wonder if I kicked it loose getting out sometime.

 

[MerlintheMad]

"Side skirt", do you mean the rocker panel or one of the under panels?

 

[crg]

"Side skirt", do you mean the rocker panel or one of the under panels?

I think I've seen it called rocker panel by you US folks. I've only ever known them as side skirts - the bit that runs under the doors between the wheel arches.

edit: doing a bit of googling, I'd think strictly speaking the rocker panel (part of the frame) is under the side skirt (plastic clip on piece).

 

[MerlintheMad]

I think I've seen it called rocker panel by you US folks. I've only ever known them as side skirts - the bit that runs under the doors between the wheel arches.

edit: doing a bit of googling, I'd think strictly speaking the rocker panel (part of the frame) is under the side skirt (plastic clip on piece).

Interesting. I only learned of the existence of "rocker panels" on here; and in the context of the plastic "side skirts" (same thing). So, what you described is a half attached side skirt? I can't even picture how that could or would occur. Even when someone has their car raised incorrectly, the side skirts don't "half" pop loose; they get dents in the edges. Yours must have come from the factory incorrectly (incompletely) attached.