Has anyone driven with the rear seats down and the moonroof open and noticed deep resonating vibrations?
I had to haul a large box and noticed this...Scared the hell out of me. Strange thing is that it goes away when either the seats are up OR moonroof is closed... or is it just my car? Anyone else notice this? If you do, do you have a wind deflector installed?

 

Nope, I never rode with the seats down but I can safely say that it is your trunk vibrating b/c air is filling your trunk and going over the the top of your roof and onto your trunk causing the trunk to vibrate. It is almost like blowing over the top of a coke bottle, same principle applies.(minored in physics)

 

I'm not sure on the name. But, it's due to the fact the air coming in has no way to escape and pressurizes when it has built up enough inside pressure it starts making the noise you are referring to. The same will happen if you have both rear windows down at highway speeds.

 

Thanks for the response guys.
I thought it was pressure related...
It's just that it got so loud, I thought it might
hit some "resonating frequency," of course that's a bit of a stretch though.

 

It might not be too far of a stretch. With the back seats down you create more air space to gather pressure than with them up, thus the louder sound. Later

 

I meant resonant frequency as in eignenvalue...
... as in tacoma-narrows bridge... as in disaster.

 

oh man, I have seen that thing before
gotta love the math behind it though

 

I have experienced the exact sensation as you describe. At times it almost hurt my ears.

 

*****
cav·i·ta·tion (kv-tshn)
n.

The sudden formation and collapse of low-pressure bubbles in liquids by means of mechanical forces, such as those resulting from rotation of a marine propeller.
*****

Dang if the same thing didn't happen in my sub last weekend down off the coast of Nantucket. I was stalkin' this russian boomer when all of a sudden he pulls this Crazy Ivan. I have to go full reverse and make this big ol' knuckle in the water. My sonarman screams at me saying we're cavitating. Damn if he wasn't right 'cause the russian sub driver sticks his hand out the window of the conning tower and flips me off. The beyotch.

Don't ask. It was the first thing that popped into my pea brain.

 

You really need to try sleeping at night...

 

Yeah, that's sound advice coming from Mr. I-don't-need-but-two-hours-of-sleep-a-night!

 

I've bumped it up to at least 3hrs lately...I must be getting old or my wife's slipping decaf in my Folgers...