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Date: Sat, 11 Dec 2004 11:42:20 -0600
From: Dennis Haverlah <clouduster@austin.rr.com>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: exhaust design question
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I would expect the Renesis engine with the split/side exhaust is not as 
irritating.  What is the experience?  I have not heard either a 13B or 
Renesis takeoff or fly-by.
Dennis H.

Charlie England wrote:

> Russell Duffy wrote:
>
>> So it appears its as much the nature of the Rotary "bark" as it is 
>> the sound level.
>>
>>  
>> I completely agree, and I've tried to get people around the airport 
>> to understand this.  Since the engine doesn't sound like a "normal" 
>> engine, everyone takes note.  Since they noticed it, they assume it's 
>> primarily because it must be louder than other engines.   This isn't 
>> necessarily true of course.  
>> Glad you got your power back.  
>> Rusty (yawn)
>
>
>
> This phenomenon is widely understood by audiophiles & (ex)sound 
> engineers. Certain frequencies, and certain harmonic structures added 
> to any sound, are much more irritating to the ear than others. The 
> 'bark' or 'edge' in the sound of a 2stroke or rotary is the harmonic 
> structure of the sound, not the actual level.  I suspect that if you 
> fed a microphone into an oscilloscope, you'd see something like a sine 
> or triangle wave from a 4stroke piston engine & something approaching 
> a square wave from a 2stroke or rotary. We  can run that experiment 
> here at Slobovia the next time we have a visit from a rotary.
>
> I suspect that's why Paul Conner's exhaust is actually a pleasing 
> sound while most rotaries 'hurt' your ears. His iron manifold is 
> probably filtering out the irritating harmonics & 'rounding off' the 
> waveform.
>
> Charlie
>
>
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