Return-Path: Received: from imf21aec.mail.bellsouth.net ([205.152.59.69] verified) by logan.com (CommuniGate Pro SMTP 4.2.5) with ESMTP id 563426 for flyrotary@lancaironline.net; Sat, 11 Dec 2004 13:59:50 -0500 Received-SPF: pass receiver=logan.com; client-ip=205.152.59.69; envelope-from=bobperk@bellsouth.net Received: from HpPavilion310n ([65.1.104.5]) by imf21aec.mail.bellsouth.net (InterMail vM.5.01.06.11 201-253-122-130-111-20040605) with ESMTP id <20041211185920.HXVR2054.imf21aec.mail.bellsouth.net@HpPavilion310n> for ; Sat, 11 Dec 2004 13:59:20 -0500 From: "Bob Perkinson" To: "Rotary motors in aircraft" Subject: RE: [FlyRotary] Re: exhaust design question Date: Sat, 11 Dec 2004 12:59:18 -0600 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook IMO, Build 9.0.2416 (9.0.2910.0) In-Reply-To: X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2600.0000 Importance: Normal Dennis, I have an AVI file of Tracy running his engine at the rotary round up that I could send you, it is 47 megs worth. If I knew how to break the file down and shorten it I would do that. As it is it would take a week to email it. Bob Perkinson Hendersonville, TN. RV9A If Nothing Changes Nothing Changes! 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 > > >>> Homepage: http://www.flyrotary.com/ >>> Archive: http://lancaironline.net/lists/flyrotary/List.html >> > >> Homepage: http://www.flyrotary.com/ >> Archive: http://lancaironline.net/lists/flyrotary/List.html