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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