Analysis: ITDG null value. Why? Any suggestions?

Replies to This Discussion

Permalink Reply by Alex Cligman on May 22, 2018 at 2:57pm

Hi there GiuBond,

Did you manage to resolve this problem, I am experiencing the same issue?

Permalink Reply by Daniel Horta on May 28, 2018 at 12:48pm

I think this and some other bugs have to do with the new release. Every time I launch the Mapping Method Tab Rhino just crash.

Permalink Reply by Arthur van der Harten on August 3, 2018 at 7:43am

Hi,

Sorry for the delay. I'm not sure what is up with the ITDG component. I will need to find some time to look at it. What it is supposed to do is Find the next large reflection following the direct sound. I think it may have stopped being effective after I changed the resolution of simulations a few years ago.

It has been a low priority item for me, so apologies about that. If you don't mind me asking, why is it important to you?

Arthur

Permalink Reply by Alex Cligman on August 5, 2018 at 9:26am

Hi Arthur,

Thanks for getting back to us, I'm using the component as part of a multi-objective optimisation study looking at how genetic algorithms can be used to develop room topologies. I’m using Ando’s Total Subjective Preference theory / Beranek’s Objective Ranking Method as the objective functions to develop a design methodology based on an acoustic morphogenetic approach. As much, ITDG is on other objective parameters I’m looking at. However, I’ve found a work around by sampling the output of energy time curve grasshopper component, filtering the output to omit low-energy samples and finding the first large reflection after the direct sound, it seems from your reply this is a suitable approach, let me know what you think,

Best regards,

Alex,

Ps. Thank you for making these components available, they are invaluable to my work, I appreciate your efforts and continued support on the forum, I would like to help out in the development process as much as I can

 

Permalink Reply by Arthur van der Harten on August 6, 2018 at 6:13am

Hi,

I think I found the issue with ITDG, and it will be released as well later in the week, as soon as I fix bugs associated with other new features.

In the meantime, have you read Tomas Mendez' PHD thesis? 

http://block.arch.ethz.ch/brg/files/phd-thesis-mendez_1411647140.pdf

He attempts the same kind of thing that you are doing. I'm very familiar with Beranek's benchmarks. I'm not as familiar with Ando's ideas. ITDG isn't used very much in practice as far as I am aware. Much more important are the issues of reverberation, loudness, and intelligibility or clarity. Spaciousness is also important, but probably second order. Because ITDG will vary tremendously with position in a room, I guess this is worth asking - how do you choose which seat to evaluate?

Arthur

Permalink Reply by Arthur van der Harten on August 6, 2018 at 8:15am

Hi Alex,
It seems we have a copy of Ando's book in our office. I will read up before I comment further on your project.
I'll let you know when I have updated the installer for you.
Arthur

Permalink Reply by Alex Cligman on August 27, 2018 at 7:54am

Many thanks Arthur,

As far as I understand Beranek's benchmarks or Objective Ranking System, ORM, has been built on Ando's Total Subjective preference theory which is essentially an objective function comprised of the weighted sum of a number of subjective parameters: IACC, EDT, bass ratio BR, G, ITDG and surface diffusivity index SDI. As I am looking at multi-objective optimisation techniques I am applying the ORM weightings post-optimisation to the pareto solutions so that each of the parameters is optimised independently of each other by a GA without penalisation. To begin with and for expediency, I am only looking at a single octave band to calculate the parameters and so I cannot calculate BR. Additionally as SDI is a material property I am not including it in my optimisation study. Leaving IACC, G, EDT and ITDG. From my initial tests, the GA I’m using for the optimisation regime struggles with IACC as it is not a hard constraint i.e. it takes the maximum value across a number of delay intervals This is why I’m looking at ITDG, although thus far it seems to be fairly quantized in its resultant value which may be  caused by an error in how I am determining its value, this is why I would like to test the pachyderm component! Do you have a projected timescale for the release of the update?

Permalink Reply by Arthur van der Harten on August 6, 2018 at 8:15am

Hi Alex,
It seems we have a copy of Ando's book in our office. I will read up before I comment further on your project.
I'll let you know when I have updated the installer for you.
Arthur