X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from mail-fx0-f216.google.com ([209.85.220.216] verified) by logan.com (CommuniGate Pro SMTP 5.3c2) with ESMTP id 3976921 for flyrotary@lancaironline.net; Sun, 15 Nov 2009 10:56:29 -0500 Received-SPF: pass receiver=logan.com; client-ip=209.85.220.216; envelope-from=msteitle@gmail.com Received: by fxm8 with SMTP id 8so5006795fxm.27 for ; Sun, 15 Nov 2009 07:55:54 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:received:in-reply-to:references :date:message-id:subject:from:to:content-type; bh=zQuNFww3Klcx4uPOMNE192bs9nYN02JzrrJFb0d6mJ4=; b=AykyhPD29yar6Up2DOxjEZjSkUCicmXT3WoJ3MnFR/r6uZQfzfftaepDTt3Fx9MuFx undBo5Aah78OpA2/C2vWXOYcgcZZXU8xh/68B0V2hyb03Zxhbi583s9Q1+WWzaS20Kjf noqUgUMGQsi0ESYBcwBzceNleEpbDfDNWlFGQ= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type; b=dTNVAZ0yph856kv5uQfMJ5LYIk6k0thIMWN69n1xv2cCBFhewk7AtqEXWRo+TJA1gS bPoqa8GitsWMLV723HSWiCOe5XBTTgTR+sb3fn26AxB5VgKOz8qPeDVPtDDej9Gl8+am r1RT8WENMqok7luektNTmTW/lhq5ODDcFt1hU= MIME-Version: 1.0 Received: by 10.204.148.69 with SMTP id o5mr2868995bkv.99.1258300552649; Sun, 15 Nov 2009 07:55:52 -0800 (PST) In-Reply-To: References: Date: Sun, 15 Nov 2009 09:55:52 -0600 Message-ID: <5cf132c0911150755l3522f230k4a538815d4d0a471@mail.gmail.com> Subject: Re: [FlyRotary] Phononic bandgap muffler From: Mark Steitle To: Rotary motors in aircraft Content-Type: multipart/alternative; boundary=0015175cda12761b7804786aedf0 --0015175cda12761b7804786aedf0 Content-Type: text/plain; charset=ISO-8859-1 Ernest, Me too, please. Mark S. On Sun, Nov 15, 2009 at 8:33 AM, Kelly Troyer wrote: > Ernest, > Please send the xcf file to me................. > -- > Kelly Troyer > "Dyke Delta"_13B ROTARY Engine > "RWS"_RD1C/EC2/EM2 > "Mistral"_Backplate/Oil Manifold > > > > > > -------------- Original message from Ernest Christley < > echristley@nc.rr.com>: -------------- > > > > Here's a question for you audiophiles on the list. How much effort is > > 10dB of muffling worth? > > > > I've expanded on my experiments with phononic bandgap filters, and I > > think I've fairly conclusively demonstrated up to 15dB of attenutation > > in the frequency ranges between 8kHz and 12kHz. I used the run-up video > > that Mike Wills provided for us a few weeks back (thanks Mike), and I > > was a little more methodical than last time. > > > > For those that don't remember, a phononic bandgap filter is created by > > geometric arrangement of dissimillar materials, with the goal of > > filtering specific vibration frequencies. It appears that 1/2" diameter > > tubes, arranged in a grid with 1" centers does a nice job of attenuating > > frequencies in the 8kH to 12kHz range. > > > > I set up my simulated muffler...a wooden shell with PVC filter > > elements. I stuck a couple speakers in the inlet side, and a > > microphone on the outlet side. In this setup, there is going to be all > > sorts of losses from the conversion from an electronic signal to sound > > in the speaker, then conversion of sound to an electronics signal in the > > microphone. Comparing the original to the recorded muffled sound, which > > I did in the first experiment, is not valid. > > > > What I did this time instead, is to compare several recordings. Each > > with one less row of filter elements than the last, until I was > > measuring an empty box. The empty box measurement is the control that > > lets me know if I'm doing anything with the array of tubes. What I > > found was that each row of tubes provide a significant attenuation in > > the frequencies between 8kHz and 12kHz. The ones that give us the > > weed-wacker sound. I determined this by taking a time sample across > > each of the 5 recordings and having Audacity plot the spectrum. > > > > I have an xcf file created by The Gimp ( a free image editing > > software). The xcf format allows you to keep an image in layers. Each > > of the plots is in a separate layer, and by playing with the opacity > > individual layers, you can easily see where the attenuation occurs. The > > file is 465kB so I can't post it to the list, but if anyone is > > interested, I'll be happy to send it direct. I'll do a writeup with > > links to the audio files "real soon now". > > > > I have attached a flatten image showing the 0 row run, against the 4 row > > run. The 0 run is the lighter purple shade. There are some some > > frequencies where the 4 row would be louder....around 4kHz and 7kHz, > > but I think the attenuation of those frequencies around 10kHz would be > > most beneficial. > > > > -- > > Ernest Christley, President > > Ernest@TechnicalTakedown.com > > > > TechnicalTakedown, LLC > > www.TechnicalTakedown.com > > 101 Steep Bank Dr. > > Cary, NC 27518 > > (919) 741-9397 > > > > --0015175cda12761b7804786aedf0 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable
Ernest,
=A0
Me too, please.
=A0
Mark S.

On Sun, Nov 15, 2009 at 8:33 AM, Kelly Troyer <keltro@att.net>= ; wrote:
Ernest,
=A0=A0 Please send the xcf file to me.................
--
Kelly Troyer
"Dyke Delta"_13B ROTARY Engine
&q= uot;RWS"_RD1C/EC2/EM2
"Mistral"_Backplate/Oil Manifold <= br>


=A0
-------------- Original message from Ernest Christley <echristley@nc.rr.co= m>: --------------


> Here's a question for you audiophiles on the list. How muc= h effort is
> 10dB of muffling worth?
>
> I've exp= anded on my experiments with phononic bandgap filters, and I
> think= I've fairly conclusively demonstrated up to 15dB of attenutation
> in the frequency ranges between 8kHz and 12kHz. I used the run-up vide= o
> that Mike Wills provided for us a few weeks back (thanks Mike), = and I
> was a little more methodical than last time.
>
> For those that don't remember, a phononic bandgap filter is create= d by
> geometric arrangement of dissimillar materials, with the goal= of
> filtering specific vibration frequencies. It appears that 1/2&= quot; diameter
> tubes, arranged in a grid with 1" centers does a nice job of atte= nuating
> frequencies in the 8kH to 12kHz range.
>
> I= set up my simulated muffler...a wooden shell with PVC filter
> elem= ents. I stuck a couple speakers in the inlet side, and a
> microphone on the outlet side. In this setup, there is going to be all=
> sorts of losses from the conversion from an electronic signal to = sound
> in the speaker, then conversion of sound to an electronics s= ignal in the
> microphone. Comparing the original to the recorded muffled sound, whic= h
> I did in the first experiment, is not valid.
>
> W= hat I did this time instead, is to compare several recordings. Each
> with one less row of filter elements than the last, until I was
&g= t; measuring an empty box. The empty box measurement is the control that > lets me know if I'm doing anything with the array of tubes. What= I
> found was that each row of tubes provide a significant attenuation in =
> the frequencies between 8kHz and 12kHz. The ones that give us the =
> weed-wacker sound. I determined this by taking a time sample acros= s
> each of the 5 recordings and having Audacity plot the spectrum.
&g= t;
> I have an xcf file created by The Gimp ( a free image editing <= br>> software). The xcf format allows you to keep an image in layers. Ea= ch
> of the plots is in a separate layer, and by playing with the opacity <= br>> individual layers, you can easily see where the attenuation occurs.= The
> file is 465kB so I can't post it to the list, but if anyo= ne is
> interested, I'll be happy to send it direct. I'll do a writeup= with
> links to the audio files "real soon now".
>=
> I have attached a flatten image showing the 0 row run, against th= e 4 row
> run. The 0 run is the lighter purple shade. There are some some
&g= t; frequencies where the 4 row would be louder....around 4kHz and 7kHz, > but I think the attenuation of those frequencies around 10kHz would b= e
> most beneficial.
>
> --
> Ernest Christley, Presi= dent
> Ernest@TechnicalTakedown.com
>
> TechnicalTaked= own, LLC
> www.TechnicalTakedown.com
> 101 Steep Bank Dr.
> Cary, NC 27518
> (919) 741-9397 >=A0

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