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From: "rijakits" <rijakits@cwpanama.net>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
References: <list-564377@logan.com>
Subject: Re: [FlyRotary] Re: exhaust design question
Date: Sun, 12 Dec 2004 12:22:59 -0500
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Finn, I see your point.

My uneducated wild guess was, that maybe the pointed pieces would not be
able to emit sound efficiently as you need some resonating surface for that
( like a big round speaker, etc.) or at least not at lower frequencies wher
we can hear it.
This whole idea was of course not ment to be a muffler for the exhaust by
itself but a "possibility" to avoid noise emitting from the muffler outside
walls.........

Thomas J.


----- Original Message -----
From: "Finn Lassen" <finn.lassen@verizon.net>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Sunday, December 12, 2004 11:10 AM
Subject: [FlyRotary] Re: exhaust design question


> Those triangular pieces are foam - some sound absorbing material. Hard
> materials like metal is not likely to absorb sound, rather they're
> likely to reflect it.
>
> Look at arcustic (sp?) ceiling pates, carpet, curtains. Then compare to
> a naked room with hardwood floors.
>
> Having the muffler, expecially a thin walled one, inside the cowling,
> and the cowling cowered with some fireproof sound dampening material,
> would undoubtedly help.
>
> Finn
>
> rijakits wrote:
>
> >A wild idea/question: How is the sound emitted from something like a
> >silencer?
> >Remember any pics of sound proof chambers - like the car manufacturers
have
> >to check source and dynamics of sound coming of their cars. These
chambers
> >are all full of triangular foam (or so it seems) to eat up the sound, as
not
> >to reflect anything and falsify the data.
> >
> >Would it work to weld triangular shaped pieces on the OUTSIDE of a
muffler?
> >.... or better has anyone any idea or tried that already?
> >I have no reason to believe that this works, but I think is worth a
thought!
> >Any sound engineers on the list?
> >
> >I remember in the old LP (music) times the very highend turntables would
> >come with an accessory: a heavy glassplate that was to be supported by
> >inverse ceramic cones or glasscones that in turn where supposed to be
placed
> >on ceramic or glass again (point down). Supposedly to not absorb any
> >frequency from the floor/suroundings and to not loose any sound to the
floor
> >either....
> >
> >I am not enough of a music conoseur to ever have found a difference, but
> >that doesn't mean it didn't work:))
> >
> >Any ideas?
> >
> >Thomas J.
> >
> >
> >
>
>
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>