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Message-ID: <002301c4d7e7$452f9520$2502a8c0@edward2>
From: "Ed Anderson" <eanderson@carolina.rr.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
References: <list-552709@logan.com>
Subject: Re: [FlyRotary] Re: Reactive vs Absorbtion Mufflers for the Rotary engine
Date: Wed, 1 Dec 2004 15:49:36 -0500
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Right on the money, Kevin.  I did not make it clear in my first message =
that I calculated the 1/4 wave length of several harmonics of rpms from =
1500 - 6000.  Then I chose the lengths that occurred most frequently in =
that matrix for my chamber lengths (distance between discs).

This gave me six  intervals for the discs spacing  ranging from 2.5" to =
11.2".  If I had a longer tube I would have picked a couple of longer =
intervals as well.

According to the theory (If I understand it correctly) what is  =
happening to deaden the sound is that the exhaust pulse encounters a =
disc (what appears to it as a solid disc) and is reflected backwards. =
When it encounters other incoming waves it interacts destructively =
thereby attenuating both waves.  If energy survives to reach the =
up-stream end of the chamber it hits that disc and reverses direction =
again, etc.   This would occur in each of the chambers between discs =
repeatedly many times a second.  So you have this chaotic mixing of the =
waves in the chambers attenuating the sound wave but not seriously =
interfering with the exhaust gas movement out the tube (hopefully).

 The sound waves are reflected from each side of each disc and a bit =
from the open end as well - however, if the discs have done their job =
the exhaust sound pulses are considerably attenuated by the time they =
reach the end of the tube.


Ed
----- Original Message -----=20
  From: kevin lane=20
  To: Rotary motors in aircraft=20
  Sent: Wednesday, December 01, 2004 12:43 PM
  Subject: [FlyRotary] Re: Reactive vs Absorbtion Mufflers for the =
Rotary engine


  Ed -- would it make sense in the placement of the reflecting inserts, =
to space them in an increasing series, so that they react to various =
frequencies, rather than trying it hit one frequency?  are the reflected =
sound waves created only from the open end, or from any surface?
  Kevin Lane  Portland, OR
  e-mail-> n3773@comcast.net
  web-> http://home.comcast.net/~n3773
  (browse w/ internet explorer)
    ----- Original Message ----- 
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML><HEAD>
<META http-equiv=3DContent-Type content=3D"text/html; =
charset=3Diso-8859-1">
<META content=3D"MSHTML 6.00.2800.1476" name=3DGENERATOR>
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<BODY bgColor=3D#ffffff>
<DIV><FONT face=3DArial size=3D2>Right on the money, Kevin.&nbsp; I did =
not make it=20
clear in my first message that I calculated the 1/4 wave length of =
several=20
harmonics of rpms from 1500 - 6000<FONT face=3D"Times New Roman" =
size=3D3>.&nbsp;=20
Then I chose the lengths that occurred most frequently in that matrix =
for my=20
chamber lengths (distance between discs).</FONT></FONT></DIV>
<DIV>&nbsp;</DIV>
<DIV>This gave me six &nbsp;intervals for the discs spacing =
&nbsp;ranging from=20
2.5" to 11.2".&nbsp; If I had a longer tube I would have picked a couple =
of=20
longer intervals as well.</DIV>
<DIV>&nbsp;</DIV>
<DIV><FONT face=3DArial size=3D2>According to the theory (If I =
understand it=20
correctly) what is &nbsp;happening to deaden the sound is that the =
exhaust pulse=20
encounters a disc (what appears to it as a solid disc) and is reflected=20
backwards. When it encounters other incoming waves it interacts =
destructively=20
thereby attenuating both waves.&nbsp; If energy survives to reach the =
up-stream=20
end of the chamber it hits that disc and reverses direction again, =
etc.&nbsp;=20
&nbsp;This would occur in each of the chambers between discs repeatedly =
many=20
times a second.&nbsp;&nbsp;So you have&nbsp;this chaotic mixing of the =
waves in=20
the chambers attenuating the sound wave but not seriously interfering =
with the=20
exhaust gas movement out the tube (hopefully).</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DArial size=3D2>&nbsp;The&nbsp;sound waves are =
reflected from=20
each&nbsp;side of each disc and a bit from the open end as well&nbsp;- =
however,=20
if the discs have done their job the exhaust sound pulses are =
considerably=20
attenuated by the time they reach the end of the tube.</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DArial size=3D2>Ed</FONT></DIV>
<DIV>----- Original Message ----- </DIV>
<BLOCKQUOTE dir=3Dltr=20
style=3D"PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; =
BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
  <DIV=20
  style=3D"BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: =
black"><B>From:</B>=20
  <A title=3Dn3773@comcast.net href=3D"mailto:n3773@comcast.net">kevin =
lane</A>=20
  </DIV>
  <DIV style=3D"FONT: 10pt arial"><B>To:</B> <A =
title=3Dflyrotary@lancaironline.net=20
  href=3D"mailto:flyrotary@lancaironline.net">Rotary motors in =
aircraft</A> </DIV>
  <DIV style=3D"FONT: 10pt arial"><B>Sent:</B> Wednesday, December 01, =
2004 12:43=20
  PM</DIV>
  <DIV style=3D"FONT: 10pt arial"><B>Subject:</B> [FlyRotary] Re: =
Reactive vs=20
  Absorbtion Mufflers for the Rotary engine</DIV>
  <DIV><BR></DIV>
  <DIV><FONT face=3D"Comic Sans MS" size=3D4>Ed -- would it make sense =
in the=20
  placement of the reflecting inserts, to space them in an increasing =
series, so=20
  that they react to various frequencies, rather than trying it hit one=20
  frequency?&nbsp; are the reflected sound waves created only from the =
open end,=20
  or from any surface?</FONT></DIV>
  <DIV>Kevin Lane&nbsp; Portland, OR<BR>e-mail-&gt; <A=20
  href=3D"mailto:n3773@comcast.net">n3773@comcast.net</A><BR>web-&gt; <A =

  =
href=3D"http://home.comcast.net/~n3773">http://home.comcast.net/~n3773</A=
><BR>(browse=20
  w/ internet explorer)</DIV>
  <BLOCKQUOTE dir=3Dltr=20
  style=3D"PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; =
BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
    <DIV style=3D"FONT: 10pt arial">----- Original Message -----=20
</DIV></BLOCKQUOTE></BLOCKQUOTE></BODY></HTML>

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