Perforated metal ceiling absroption

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Tom Harper - 22 Dec 2004 14:40 GMT

Hi all

I am currently building an EASE model for a building that is using a
perforated sheet metal ceiling, minimum 25% Open Area with no backing
material. The main purpose of the ceiling is to hide the duct work in
the void etc.

I figure that the main source of absorption in the room comes from the
mineral wool to be placed on the slab soffit but I am sure that the
perf metal ceilng will have some effect, I am just not sure what and
how much.

I have done a search on past posts and note that Eric and Angelo have
discussed this in the past but I could find any actual values to put
into my model.

Please help! Thanks in advance, need to get some sort of result soon.
Tom

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Asbjørn - 22 Dec 2004 18:23 GMT

With fairly large holes and no extra flow resistance (mineral wool or cloth)
the absorption gain will be minimal.
Remember that the ductwork also may have some absorption.
You could try out WinFlag, an expert program that calculates acoustical
properties for layered structures with defined properties. See
http://winflag.com/

Asbjørn

> Hi all
>
[quoted text clipped - 14 lines]
> Please help! Thanks in advance, need to get some sort of result soon.
> Tom

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Noral Stewart - 23 Dec 2004 11:53 GMT

Check this out.

http://www.iperf.org/acoustic.htm

> Hi all
>
[quoted text clipped - 14 lines]
> Please help! Thanks in advance, need to get some sort of result soon.
> Tom

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Tom Harper - 24 Dec 2004 03:44 GMT

Noral

Thanks very much.

I would seem that with a fairly large backing space (1 -2 metres) and
about 25 % open area the peak abosorption for the perforated metal
would be in frequncies well below 50 Hz or so.

Not much help to me at the moment but good information to keep in mind.
Cheers

Tom

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Natural Science Forum / Physics / Acoustics / December 2004

Perforated metal ceiling absroption