acoustic Simulations
Acoustic simulation experiments to analyze the design, configuration, quantity, and location of mycelium-based panels.
Our perception of sound is dependent on our physical environment and is unique to the type of materials with which sound waves interact. Much of the sound that we hear arrives indirectly, meaning sound waves reflect off the many geometries of our environment before they reach our ears (Shinn-Cunningham, 2003). Thus, the placement and articulation of interior and exterior surfaces must be thoughtfully designed for acoustic purposes. Acoustic panels can be used as a mitigation strategy to help enhance the acoustic quality of a space. Acoustic panels also offer a large degree of customization, allowing for modifications depending on the design intent.
This research outlines the acoustic simulation and analysis of sound absorption panels made of mycelium-based composites. Given that mycelium-based composites are novel materials and lack comprehensive acoustical data, sound absorption tests are first performed to gather material-specific data on mycelium-based composites and their acoustic performance. This material-specific data is then used as an input for room acoustic simulations, using ray-tracing and image-source methods. The simulation results allow for an objective comparison between the design, configuration, quantity, and location of mycelium-based panels. This study intends to explore the use of acoustic simulations as an architectural strategy in the early phases of design.
Publications:
Walter, N. & Gürsoy, B. (2023). Simulating Acoustic Performance of Mycelium-Based Sound Absorption Panels. In Digital Design Reconsidered - Proceedings of the 41st Conference on Education and Research in Computer Aided Architectural Design in Europe (eCAADe 2023) - Volume 1, Graz, 20-23 September
Simulation tools
Pachyderm was selected to run computer simulations and acoustical analysis. Pachyderm is an open-source acoustic simulation plugin for Rhino and Grasshopper that combines ray-tracing and image-source methods for auralization and analysis. It uses the geometric surfaces defined in Rhino combined with material data inputs to analyze acoustic parameters such as reverberation time, sound clarity, sound pressure level, speech transmission index, and others.
The comparative parameter for acoustic analysis is reverberation time. Reverberation time refers to the amount of time it takes for the sound pressure level to decrease 60 dB once the sound source stops producing sound (Adams, 2016). This metric is directly related to the volume of enclosed space and the absorption coefficients of the surface materials.
Simulation setup
The environment of the simulation experiment consists of a shoebox geometry, panels attached to an interior wall, a sound source, and a sound receiver. The shoebox geometry defined is 18’ x 14’ x 10’ in length, width, and height. The panels have a total surface area of 60 ft2 on the short end of the room.
Materials are assigned to each interior wall, floor, and ceiling within Pachyderm’s material editor. The sound absorption coefficients of the best performing material derived from these acoustic tests are assigned to the mycelium panels. Drywall is assumed for the interior wall finishes, and the sound absorption coefficients are inputted reflecting 1/2″ plasterboard paneling on studs. The ceiling is assumed to be a commercial absorption ceiling, common in educational facilities. The sound absorption coefficients used are from Armstrong® Ceilings, specifically the Fine Fissured™ School Zone® ceiling panel (Armstrong Ceilings, n.d.). The sound source is a geodesic source assigned to a point, and the sound receiver is defined as a stationary receiver assigned to a separate point.
Testing Tile Configuration Patterns
The first set of simulation experiments tests the effect of tile aggregation pattern on reverberation time. All panels are 12” x 12”. Using the settings explained above, the aggregation patterns shown below are simulated in Pachyderm. The patterns are chosen to explore how the surface area of panel extrusions impact reverberation time.
Testing Three-Dimensional Qualities of Panels
This simulation experiment tests the three-dimensional qualities of the panels, while still maintaining the same panel depth. These panels all have an average thickness equaling 1.5”, which is the depth of the samples tested in the impedance tube. All panels are 12” x 12”. To assess whether the panel geometry affects the reverberation time in the room, a flat panel with a depth of 1.5” is also simulated to compare against the more complex panels. Additionally, to assess how non-Truchet panels perform, Mogu’s Kite geometry (Mogu, n.d.) is also simulated with our material data.
Testing the Number of Panels
The third simulation experiment tests how the number of panels in the room affects reverberation time. Using the Extruded Truchet Tile, this experiment compares the reverberation time of 60 panels, 72 panels, and 96 panels, all located on the short end of the room.
Testing Tile Configuration Patterns.
The fourth simulation experiment tests how the location of panels in the room affects reverberation time. Using the Extruded Truchet Tile, this experiment compares the reverberation time of 96 panels in different locations in the room. The sound source and receiver remain in the same position. The tested locations are: (1) all 96 panels on the short wall, (2) 60 panels on the short wall and 18 panels on each adjacent long wall, (3) 48 panels on each short wall, (4) 48 panels on each long wall, (5) 48 panels on a short wall and 48 panels on a long wall, and (6) all 96 panels on the long wall.
This experiment sets out to explore how the design, configuration, quantity, and location of mycelium-based panels affects their acoustic performance. Through acoustic simulations based in geometrical acoustics, we are able to have an objective comparison between theoretical designs, rather than fabricating many acoustic panels and testing them using a full-scale room acoustic analysis. Pachyderm proves to be a useful Performance-based Design tool, allowing for acoustic experimentation to be efficiently done in the early stages of design.
The results of the computer simulation experiments demonstrate that the mycelium panels significantly reduce the reverberation time compared to the empty room. The results also demonstrate that the specific design and configuration of the panels do have an effect on the overall acoustic performance of the space, indicating that the design of acoustic elements should be considered.
References
Shinn-Cunningham, B. (2003) ‘Acoustics And Perception Of Sound In Everyday Environments’, Proceedings of the 3rd Int. Workshop on Spatial Media, Aisu-Wakamatsu, Japan, Mar. 6-7, 2003.
Adams, Tyler. (2016). Sound materials: A compendium of sound absorbing materials for architecture and design. Frame Publishers.
Armstrong Ceilings. (n.d.) School Zone Fine Fissured. Retrieved January 16, 2023 from https://www.armstrongceilings.com/commercial/en/commercial-ceilings-walls/school-zone-fine-fissured-ceiling-tiles.html