You probably have better understanding than most!

Older cars had no dedicated exhaust vents. Most of them were leaky enough that they were not missed. VWs were the exception since they were very well sealed (they actually floated for quite a while if you drove into water) so the doors would close easier and the heater would work better if you opened a vent window slightly.

Modern cars have dedicated exhaust vents. The Fit's are located below the hatch opening. They're great for closing the doors, but don't really help resonance issues.

My theory is that modern cars don't have as much turbulent detached airflow around their windows so it is easier for them to build up a noticeable resonance. Older cars trip the airflow right at the front of the car so there is little laminar flow at all.

 

Normal. For hatchback/suv anyway. Tesla model X exhausts air in the back to avoid it

 

Works for me, but IIRC, '60s VWs had no roll down rear windows but swing outs with hinges and latches, much like the front vent windows.

 

Air coming in the rear windows has nowhere to go except back out the rear windows, not pleasant for anyone involved. Use your fan.

 

Perfectly normal...it is called Helmholtz resonance:

https://en.wikipedia.org/wiki/Helmholtz_resonance

 

I have never owned a car that doesn't do this...

 

My experience has been that the more aerodynamic the car, the more pronounced this phenomena becomes. Interestingly, my last couple cars had euro rails for attaching roof racks. With the roof racks removed, the rear window resonance was really bad, requiring the front window(s) to be cracked. But, with the roof racks installed, the racks messed up the airflow such that I could put the rear windows down without resonance.

 

it happens in many cars (hatchback cars mainly) I use to get that in Nissan Versa

 

My recently acquired Hyundai Accent Hatchback had that noise problem until I installed WeatherTech rain guards.
My wife's Honda Accord also use to have the same noise issue with the back windows down but after we installed the WeatherTech rain guards we no longer have that noise problem.

 

My 2006 BMW has the same issue. My 1995 BMW does not.. Old one has pop-out windows like an old BUG, new one is a 4 door. And It does the resonance with or without the sunroof open.

 

I hate to say it, but this does remind me of the old joke:
Patient, "Doctor, it huts when I do this."
Doctor, "Don't do it."


Seriously, I can't think of any reason I'd want to drive with the front windows up and the rear windows down. FWIW, my '09 Fit did the same thing (I discovered it while playing around with the window switches). Other cars I've owned might have done it as well, but I never found out as the 2 Fits are the only cars I've ever owned with power windows that I could roll down the rear windows while driving.

 

Exactly, this is a result from cars that are very slippery in terms of their aero to gain greater fuel economy. Old cars didn't have his issue because they were smashing the wind.

You can only really drive around in modern cars with the windows down at very low speeds.

 

Same phenomenon with my '08

 

My '12 Sport and our Prius do the same thing.

In Paris, there is a fully automated subway line that has upper windows that you can tilt inward when it is hot, and it maximizes airflow through the train and everyone gets a nice cooling breeze.

The Fit is probably too narrow to accommodate inward-folding windows safely.

But that subway trick is cool!

 

In the Fit EX, there is a spring-loaded "lip" at the front of the moonroof that pops up when the moonroof glass is opened. Just playing around with the roof open yesterday, I reached up and pulled the "lip" down with my hand (retracting it back into the car). At 40MPH, instant buffeting was the result.


That "lip" (which has a "castellated" profile) is there to induce sufficient turbulence to stop the buffeting.

 

I discovered the same thing tonight! I had all the windows closed and the moon roof open. At 30 mph, when the "lip" is down, there is a distinctive percussive oscillation. This is my first car with a moon roof. Do moon roofs in all cars have the "lip"?

 

I've seen this in many cars, not just the FIT. A bit of opening in a window can make it sound like parts are blowing away.

As another post mentioned, tinkering with window opening amount can end the noise.