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Date: Tue, 19 May 2009 11:00:24 -0400
From: Ernest Christley <echristley@nc.rr.com>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: 20b Exhaust
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William Wilson wrote:
> Well that is sure spiffy.
>
> In addition to reducing high frequency noise, it looks like the filter 
> smooths out the frequencies in the lower regions which will make for a 
> less "noisy" sounding exhaust even if it's not actually any quieter.  
> It would probably also be easier for ANR headsets to filter out.
>
> You could try experimenting with ceramics.  I think PVC and wood have 
> a natural muffling effect that metal pipes won't have.  Ceramics can 
> withstand the high temperatures and may be easier to work with, 
> especially in development stage, since clay is very easy to shape.  
> Plus, they do it on the F-117, so it's got to be good.
>
One step at a time.  The first step is to determine if there is actually 
anything to this cockamamy idea that an arrangement of objects can 
filter sound.  The next step is to build a prototype from materials that 
have been used successfully and see if it is effective.  If that works 
well, I might consider novel materials.

So now I will test the empty box with the frequency sweep, and then I 
will run some test using actual recorded sounds from an un-muffled 
rotary.  I think I have a recording here somewhere.

-- 

http://www.ernest.isa-geek.org