Re: 98 Passat Wagon - Helicopter mode

[John + Joanne Baker <jb@access.digex.net>]

On Wed, 20 May 1998, Don Hoefer wrote:
> Oh yes.  Think of an organ pipe.  A long tube with a hole in it.
> It will resonate at it's natural frequency.  The bigger the pipe
> the lower the frequency.  Cars are pretty big.  My Coupe must do
> three or four hertz.  To stop the pipe from vibrating, drill a hole
> in it to set up canceling resonances, or open a window in the car.

That would explain why I still hear it a little with a back
window open - it's being cancelled, but not completely.

The open window also solves the ear popping.  With the windows
shut, I feel like I am in a pressure suit!  I wonder if the
car is airtight, and there's nowhere to relieve the pressure
of the air rushing in the roof.  Maybe putting a vent somewhere in
the car would help reduce both the resonance and air pressure.

John