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Date: Tue, 22 Sep 2009 09:30:12 -0400
From: Ernest Christley <echristley@nc.rr.com>
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Mike Wills wrote:
> One thing I did notice on this flight. Taking my feet off the rudder 
> pedals and placing them flat on the floor changes the vibration 
> characteristics of the floorboards and affects the operation of the 
> ANR circuit in the headset. In general I norice the ANR is much more 
> susceptible to being confused in the RV with the higher freq noise 
> environment.
This reminded me of something, and I had to go look it up.

Check your local library, or maybe just ask around, and get a copy of 
Make Magazine, issue number 16.  Look on page 122.  It describes the 
setup of a Chlandi plate, a technique for making vibrations visible.  It 
would be a neat way to investigate your floorboard's resonance and 
explore ways to dampen the sound without the weight of the brute force 
padding technique.

I have to get my plane flying first, but my experiments will center 
around the use of toolbox liner covered with trunk liner carpet.