Rear windows open and drumming sound

I think you will notice this is any car. It certainly happens in my Odyssey. Try lowering the front windows a little bit at a time, I think you will find the noise goes away. Maybe just too much air pressure with no where to go?

 

My wife's PT does the same thing and it's damn annoying. As near as I can tell you're setting up a resonance in much the same way as when you blow across the end of a bottle. I think that some venting in the rear of the cabin would relieve the problem.

Bummer I was hoping that the Prius didn't have this 'feature'.

 

Unfortunately it does. It's very unsettling, but playing around with the windows can usually stop it.

More discussion here:
http://www.priuschat.com/forums/viewtopic.php?t=1763

 

I have noticed the same thing. I had a car years ago which did not do this, and it was nice because I could drive with the front windows up to avoid air from hitting my face but still citculate enough air through the rear windows. The first time I tried this in my Prius I thought that a helicopter was hovering over the car. :roll:

 

It's an "organ pipe"-like resonance of the air inside the car. Change the size of the opening, change the car's speed, or experiment with opening one or more other windows to stop it. Adding passengers can affect it also.

 

I've found that lowering the left rear window about 5 inches as well as the right front window at least a couple of inches has eliminated all wind drumming effects at all speeds I've driven.

 

Sure does, my girls always complain if I open the windows much. They always close theirs, they don't like the wind in their faces. Must not have been dogs in a former life!

 

Yup. The official technical term for it is ... believe it or not .... "Helicoptering".

The owners manual for my Dodge Ram says to adjust the window openings until the noise stops - either open or close other windows or adjust the open one a little. I'm not sure without looking, but I think it is mentioned in the Prius manual also.

The strange thing is, in all my earlier cars (before the 1990's), I never had that happen, no matter how I arranged the windows. Now it seems all cars do it. I wonder if it's the design for better aerodynamic airflow with the windows closed. I think what happens is there is an alternating cycle between pressure and vacuum inside the cab due to airflow going past the window. I can feel the pressure changes in my ears when it happens.

 

I would say this is the first car I've had this happen in, but that's only technically true. All my other cars either only had front power windows, or no power windows. I'm just enjoying the fact that I myself can roll down the back windows as a driver at all!

-m.

 

Until a few years ago cars had a black or chrome gutter over the windows that collected the water running from the roof down the sides of the car. That gutter is now built into the roof and the glass is flush with the sides of the car. Perhaps this causes the helicopter effect.

Some people install tinted plastic shades over the windows. I wonder if this eliminates the sound.

 

Think Lamanar Flow, the air flow over and around the car is very close to the actual body of the car. To get a CD of .26 the car is designed to have the air tightly follow the shape of the car and anything to upset the airflow will cause the air to change directions and start all sorts of strange flow patterns, causing all kind of noises etc. It's been said up to 35-40mph windows down for air circ. and above that speed more efficient to operate the climate control system.

 

My Peugeot 206 three door hatchback also has this helicoptering problem, but only if you lower the passenger side window all the way without opening the driver side window as well.