ask for the insertion loss for RC ducting

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tkhsu2@gmail.com - 14 Jul 2007 03:16 GMT

dear Pals:
Did anyone know the information about the insertion loss on RC tunnel.
We have some data from the ASHRAE and SMACNA. But they all for the
metal ducting.
Not for the RC ducting.

Edward

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Angelo Campanella - 14 Jul 2007 16:05 GMT

> dear Pals:
> Did anyone know the information about the insertion loss on RC tunnel.
> We have some data from the ASHRAE and SMACNA. But they all for the
> metal ducting.
> Not for the RC ducting.

Please define "RC".

The only specialty duct I am aware of is the flexible duct.
That insertion loss depends on the flexibility.
More flexibility (softer walls) = more IL.

Ang. C.

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tkhsu2@gmail.com - 14 Jul 2007 16:14 GMT

> tkh...@gmail.com wrote:
> > dear Pals:
[quoted text clipped - 10 lines]
>
> Ang. C.

thanks for Ang. C.
RC means "reinforce concrete", use in the exhasut tunnel for the
subway.

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angelo Campanella - 15 Jul 2007 23:06 GMT

>>>Did anyone know the information about the insertion loss on RC tunnel.
> RC means "reinforce concrete", use in the exhasut tunnel for the
> subway.

    The only quick reference is the absorption coefficient for bare
concrete, which is very little. Then there is the matter of absorption
for a given length of tunnel. The soil on the bottom surface will
provide the greatest absorption.

    Beyond that, you will need to make your own measurements of aound
absorption.

    As you have expected, someone here may have experience in the matter.

    Except for soil, we usually esxpect no abssorption for concrete other
than the 0.01 to 0.05 value quoted for concrete room surfaces.

    The only absorption you can rely upon in such a tunnel is that which
you install purposefully to reduce reverberation.

    Freshly cut rock will have a little more absorption because of the many
open fissures. If it is plastered over, then that absorption disappears.

    Angelo Campanella

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tkhsu2@gmail.com - 19 Jul 2007 16:44 GMT

> tkh...@gmail.com wrote:
> >>>Did anyone know the information about the insertion loss on RC tunnel.
[quoted text clipped - 21 lines]
>
> Angelo Campanella

thanks

edward

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Tom Harper - 20 Jul 2007 21:10 GMT

On Jul 14, 10:16 am, tkh...@gmail.com wrote:

> dear Pals:
> Did anyone know the information about the insertion loss on RC tunnel.
[quoted text clipped - 3 lines]
>
> Edward

If you want to predict Transmisson Loss due to a long tunnel you could
consider theory on Long Flat rooms. Engineering Noise Control by Bies
and Hansen has a good section on this an includes tunnels

Tom Harper

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Natural Science Forum / Physics / Acoustics / July 2007

ask for the insertion loss for RC ducting