Small room ratio calculations

[Today's Guest]

What started as a search for a good practice room design is ending up to be an interest to create a dynamic calculation comparing various established methods. In particular I’m trying to replicate the geometric modal approach by M.M.Louden (71) results as well as the Cox&Antonio (2000) paper using the image source model approach. Off to a bad start with the unfortunate reply from my research librarian: "Your request has been cancelled by the interlibrary loan staff for the following reason: We have exhausted all possible sources. No library is able to supply this item." I have essentially given up on tracking down Louden’s paper and I’m trying to piece together what I can from online forums such as this one! I have been able to get a fairly good qualitative reproduction of the results but the quantitative results are off. At this point I assume details are important as I have noticed significant variations in the standard deviation of the modal spacing’s as a function of the frequency cutoff as well as the choice of “spacing metric”. If anyone has some ideas, comments, anything I’d appreciate it!! At this point I’m just about ready to try anything!

[Geluidforum]

I Googled this: http://forum.studiotips.com/viewtopic.php?t=3148

Eric is a regular contributor here, so he'll most likely be able to explain more!

The article should be in Acustica issue 25-5 (1971)
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[Today's Guest]

Success!! My librarian came through and somehow did manage to get me a copy of Louden’s paper despite the bleak outlook. It is amazing how the details can fix everything! The key thing was to use the Rayleigh asymptotic formula of eigentones as a reference/ideal spacing when finding the standard deviation of modal frequency spacings. Reproducing Louden’s results was then trivial. I was surprised though to find much lower standard deviation than Louden once the gird mesh size was reduced. This is certainly meaningless when ratios have multiple decimal places but I wonder if anyone is aware of some smoothing/interpolation scheme that is suitable? A gradient weighted smoothing seems appropriate…. I still would love to hear from folks who have experience with this approach and can give me some further insight!

Now, time to address the Cox paper and the image source model. Still no progress on building the proper energy impulse response so I can FT to the power spectrum. Help would be great here as well!

[Eric Desart]

Can you upload this Louden Paper somewhere please?

[Greatday]

[Eric Desart]

Greatday,

Can you email me that paper if Geluidforum (the administrator of this site) emails you my personal email address?

With many thanks ...

[Greatday]

No problem, will do!

[Eric Desart]

Geluidforum,

Wil of kan jij mijn emailadres door emailen aan Greatday?
a.u.b.?

[Geluidforum]

Al gebeurd! / Done!

[Eric Desart]