New Porous Absorber Calculator

[prairiedog]

Hi All

I've recently written a porous absorber calculater for my own use and have decided to make it available over the internet. Here's the link:

Porous Absorber Calculator

I believe that it's working correctly and is stable but would appreciate some feedback if you have any problems with it.

Hope you find it useful.

Demetris

[Hannes_F]

Very cool, man!

[avare]

Originally Posted by prairiedog

Hi All

I've recently written a porous absorber calculater for my own use and have decided to make it available over the internet. Here's the link:

Porous Absorber Calculator

Thank you!

Andre

[DanDan]

Cool and thanks Demetris.
DD

[prairiedog]

Thanks to Hannes for pointing out some shortcomings of the Delany/Bazley model. I have now added some more recent models including the Miki model suggested by Hannes.

Demetris

[laagman]

Hi prariedog, thanks for sharing your tool!

Can I use your calculator to predict the absoption of a SSC? If yes what should I enter as "thickness"?

There must be a table somewhere with flow resistivity values of fiberglass and rockwool for the usual densities. Anyone?

[avare]

Originally Posted by prairiedog

Thanks to Hannes for pointing out some shortcomings of the Delany/Bazley model. I have now added some more recent models including the Miki model suggested by Hannes.

Thank you once again Demetris.

Andre

[localhost127]

Originally Posted by prairiedog

Hi All

I've recently written a porous absorber calculater for my own use and have decided to make it available over the internet. Here's the link:

Porous Absorber Calculator

I believe that it's working correctly and is stable but would appreciate some feedback if you have any problems with it.

Hope you find it useful.

Demetris

thanks!

[prairiedog]

Can I use your calculator to predict the absoption of a SSC? If yes what should I enter as "thickness"?

Not really. You can probably get a rough idea of absorption by modelling a flat absorber of half the depth but it won't be very accurate. This approximation might, however, help you to decide on a suitable material to use.

Demetris

[tlindaas]

Is there something to say about the different models/formulaes? Like, if your situation is this, choose this model, and so on.

[amishsixstringe]

How hard would it be to put a few common materials in as presets? Such as: "OC705 - gfr 45000" etc...?

This thing is awesome by the way! Thanks!

Neil

[DanDan]

Awesome indeed.

Here's a collection of GFRs from around the world.

Common Gas Flow Resistivity numbers.

With respect I wouldn't favour presets. e.g. OC appears to be impossible to get outside of the USA.

DD

[amishsixstringe]

Hey Dan, Thanks for that link. I have been looking for something like that for a long time now.

Thanks to all of you!

Neil

[andrebrito]

Thanks a very nice calculator thanks !

[prairiedog]

Originally Posted by tlindaas

Is there something to say about the different models/formulaes? Like, if your situation is this, choose this model, and so on.

Sorry it's taking me so long to reply to your questions, I've been very busy the last couple of months. I gave a short answer in the Q 4 Avare thread where I suggested that Miki and Allard/Champoux are good choices. I will expand on it a little here.

In most cases the differences between models are small and probably less than the manufacturing tolerances of the materials being modelled, however some of the models do have specific advantages/disadvantages which you may want to take into account.

The Delany/Bazley model has been widely used for many years and is known to give reasonably accurate results most of the time. It is also well behaved outside of its applicable range. However, some of the other models will give more accurate results, particularly at low frequencies and when modelling multi-layer absorbers.

The Mechel/Grundmann models are generally accurate but are not well behaved outside of their applicable range, particularly at high frequencies.

The Komatsu model is relatively new, and as far as I know, has not yet been widely used. Although the author claims that his model is an improvement over the Delany/Bazley and Miki models, I don't feel that he presents enough evidence to show that this is really the case. Given that the results at low frequencies don't match the other models, I would be reluctant to use this model until further research has been done.

The Miki and Allard/Champoux models give accurate results over a wide range of input parameters and have been widely used for many years. I don't have a strong preference but if pushed I would say that Allard/Champoux may be a bit more accurate. This is just an opinion based on the way the models were developed. Others may disagree.

How hard would it be to put a few common materials in as presets? Such as: "OC705 - gfr 45000" etc...?

Not too difficult but I am currently very busy so it may be a while before I get a chance to look at this. I would retain the option to enter a flow-resistivity value. Hopefully that would keep Dan happy.

I do have a new version on the way with some nice enhancements but haven't had time to thoroughly test it and prepare documentation. I'm hoping to have more free time next month and will do my best to make the new version available as soon as I can.

Thanks for your interest and for all the positive comments.

Demetris

[tlindaas]

Thanks for the explanation Demeteris!