Designing the chairs and mapping the listening area

Hi Arthur,

Question about design seats. I watched Prof. Isak Worre Foged’s videos.

I understood how to display the results in the listening area. But in doing so, the Concert hall chairs are not drawn.

If I wanted to model the chairs, in order to insert the correct material (with the relative absorption coefficient), what is the listening area? can I still see the results?

Can we design the chairs and consider them in the simulation, and visualize the results with a mapping?

If you model the chairs, under the mapping surface, are the chairs considered in the simulation?

I would be answerable, no. But then, the problem remains that chairs can not be considered in the simulation. In this way they do not contribute to the calculation of the RT, ect. How should I do?

Thanks a lot,

Kind Regards,

Giulia

Replies to This Discussion

Permalink Reply by Arthur van der Harten on February 7, 2018 at 7:03pm

Hi Giulia,

Theater and concert hall seating are among the hardest part of acoustical modelling. Standard practice is to model seating areas just as you see in the Round Robin 2 model that you have posted a picture of in your post. The reason is that sound has larger wavelengths than light.

With a light rendering model, energy can be said to reflect specularly, relative to their geometry, because the wavelength of light is inifinitesimally small relative to any object you might have modelled. With sound, energy may travel and reflect diffusely, or move around objects, depending on the scale of those objects. Think of the fundamental equation of frequency to wavelength - speed of sound = frequency X wavelength. Using that, you can see that a wave in the 125 hz octave is about as tall as a human being (or maybe a little taller) and would easily move around your body, not being reflected at all. A wave in the 1000 Hz. octave band is as big as your forearm, and might reflect specularly from your torso. A wave in the 4000 hz. octave band is about as long as your index finger, and might reflect off of your torso, or even your head.

Similarly, if you were to model the seats explicitly, it might be relatively accurate at very high frequencies (say 4000 hz. and above) but that is a very small part of the answer. Consensus in the field is that the most accurate way to model the seats is with a flat plane, raised to about shoulder height, and then with scattering coefficients applied to represent the varying effects of geometry on sound. I tend to use low coefficents below 250 hz. (say around 30%) and high coefficents above 250 Hz.(90%).

Absorption depends on the seat which was chosen. This is often a good area to use for a model calibration based on measured reverberation time.

Arthur

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