Reabsorption – parametric acoustic panels


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reabsorption – the process of absorbing something again

Oxford Languages – Google Dictionary

1. Goal

  • making acoustic panels from moulded recycled paper with optimal topology (in terms of sound scattering and absorption)
  • composing a versatile pattern that treats a wide range of frequencies with only 1-3 types of moulds
    • using Grasshopper and dedicated plugins as a helping tool for the whole design process
      • topology design
      • topology acoustics analysis (Pachyderm)
      • mould design
      • assembly simulation (Wasp)

    2. Approach

    Evolutionary optimization combined with acoustic analysis is unaffordable time- and resource-wise.

    This is why Grasshopper with Pachyderm acoustics analysis plugin were used to manually test several topology designs for best scattering properties and then further optimize the best option.

    2.1. Panel designs

    The repeatable pieces were created using Grasshopper and basic Rhino geometry as parameters, making sure the pieces fit together.

    • non-variable patterns (control group)
    • variable patterns
    • random patterns

    2.2. Testing the panels

    Fixed parameters: size and shape of room, speaker and receiver position, material absorption coefficients and other acoustic analysis settings, panels placement number, thickness and approximate size
    Variables: Panel topology

    2.3. Pattern Assembly with the Wasp tessellation plugin

    3. Acoustic analysis – scripting

    Input: speaker, receiver, room and panels geometry, materials coefficients (coefficients need to be set in Rhino; as no data on the exact type of shredded, recycled paper could be found, coefficients from studies on similar materials were used – links below)

    Analysis methods (ray tracing and image source) and relevant settings:
    ray count around 25x room volume, the higher the settings, the more precise (but longer) calculation

    Output: reverberation time – the lower the more effective topology

    3.1. First results

    returned values negligibly similar with reverberation time varying just by 0.01-0.05 sec

    3.2. Changing parameters

    3.3. Bigger scale and problem with meshes

    up-scaled the room and used maximally different absorbing geometries (to test if script returns any results at all);
    Unfortunately, somewhere during changing the settings “problem with meshes” error started appearing and I was unable to tell what the problem was.

    3.4. New acoustics script

    After rewriting the script, the calculations were running considerably slower than in the previous attempts;
    tried using a different computer with higher RAM in case the problem was my machine; tried other Rhino versions, too.
    Unfortunately, the analysis still exceeded reasonable calculation time. This depleted my options for further exploration of the problem.

    4.5. Summary of results

    The overall process returned results which differed very slightly. Yet, I’m not able to tell whether that’s an issue of the script, the input geometry or the panels design being insufficient.

    7. Pachyderm for Rhino

    Besides Grasshopper, Pachyderm operates in Rhino itself as well. I tried this option, too, in addition to the scattering analysis option, that, although still an experimental part of Pachyderm, is available there.
    Tried on the other computer as well.
    These attempts, however, returned similar results to the ones before.

    8. Wasp tessellation

    Finally, I also created a simple tessellation script using the Wasp plugin. It previews the complete composition of panels on a custom wall, avoiding obstacles like windows and doors, and gives the number of panels needed, based on the size of the pieces.

    9. What’s next

    The script could be rewritten again, following one of the tutorials available online (link below), to avoid any issues with geometry, computation time or mistakes that were overlooked. It might also work better in the Rhino 8 version, once it is fully developed and stable. If the issues were to be overcome, the process could be further developed, possibly expanded to generative design and automated optimization

    Overall, however, Pachyderm provides a very useful tool for the still new computational design in architecture. The plugin is definitely worth exploring, developing and looking for its potential new applications, also in combination with other add-ons.

    Many thanks to the authors of both plugins for their work developing and providing these tools for free.


    Pachyderm tutorials:

    Material studies and coefficients: