This research focuses on developing sustainable alternatives for acoustic panels and noise-mitigating structures in infrastructural and urban environments. It addresses both the environmental impact of current solutions and the effects of urban noise stress. Through material and product development, different strategies are explored to absorb traffic and urban noise and improve the quality of dense urban environments.

The initial literature research examines noise mitigation strategies, existing acoustic materials and products, sustainable materials for the built environment, and Key Performance Indicators for assessing newly developed solutions. The aim is to create a durable, low-carbon alternative to commonly used outdoor products made from concrete, glass, perforated aluminium and mineral wool.

The material research focuses on porous fillers, foamed materials and perforated structures. Parameters such as pore size, panel thickness, surface texture and density influence sound absorption. Samples were tested with an impedance tube across high, mid and low frequencies, with the main focus on 400 to 2500 Hz, considered a critical range for human noise disturbance. Grasshopper with Aeolus was also used to support design decisions and explore acoustic panel geometries for urban scenarios.

Various material samples were produced to maximise sound absorption within the target frequency range. Porous fillers, foamed samples and perforated panels were developed and assessed. Foaming procedures, perforation rates and backing cavities were explored in relation to Helmholtz resonance. Variables such as particle size, heating temperature, baking time, filler volume and weight fraction significantly affected both acoustic and material performance. Temperature variations between 100 and 160 °C were investigated, and each material was evaluated using a grading tool.

The results indicate that several developed configurations could become viable alternatives to current sound mitigation products. Perforated materials combined with a reed structure and cavity showed strong sound absorption based on the Helmholtz principle. Foamed furfuryl alcohol materials, particularly furan resin from Biorez, also demonstrated relevant absorption within the target range, with sound absorption coefficients of 0.8 to 0.9 achieved in several frequency bands.

Additional tests assessed flexural strength, impact resistance, moisture uptake, UV resistance and weather resistance. The best-performing final product combined a perforated 8040 Fire Hemp front panel with 20–30% open area, an absorbing backing material and a 40 mm cavity. A 100 mm reed layer was used in this study. Among the foamed materials, the cork-based S3 sample achieved a sound absorption coefficient of 0.85 at 1500 Hz.

To conclude, the research demonstrates a promising circular strategy for low-carbon acoustic products in infrastructure and urban environments.
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The research question this paper answers is: ‘’How can felled urban trees be processed into tailor-made load-bearing architectural elements using computational optimization?’’. This question is relevant because urban trees are currently an under-utilized material. The built environment accounts for up to 40% of the energy demand. Timber structures can have a Global Warming Potential ten times lower then steel structures, when taking the embodied carbon into account. This paper has found that a best-fit heuristic for 3D bin-packing could result in a 30-40% utilization of roundwood timber for lead-bearing elements. Metaheuristics can improve the utilization by several percent. The trees marked for felling in Rotterdam could supply enough wood in half a year to supply for both small scale residential dwellings as well as for large scale commercial buildings. These findings are a prove of concept for a framework that utilizes urban trees into tailor made load bearing elements. ... Read more

This study presents a computational and experimental framework for translating arbitrary doubly curved surfaces into 3D-printed, deployable structures based on programmable mechanical metamaterials. A rotating-polygon auxetic lattice is employed for its ability to expand or contract while preserving in-plane geometry. A dynamic-relaxation workflow implemented in Grasshopper/Kangaroo links flattened and target configurations through a global equal-length constraint, automatically resolving element dimensions and hinge rotations. This approach is validated on test shapes with three types of curvature: mono-, syn-, and anticlastic. Physical models of these test shapes were printed to demonstrate the feasibility of the method.
In addition, the potential for scaling the system to full-scale structures was explored through large-format additive manufacturing. Deployment techniques were investigated, and discussions with industry experts informed decisions on manufacturability and material selection. Full-scale printing trials were conducted to balance the flexibility required for compliant hinges with the rigidity needed in structural elements.
Finally, the developed method was applied to a case study: a temporary shelter for festivals and events. A deployable design was created, and optimisation strategies were explored for both the surface geometry and the applied lattice grid. Finite element analyses were performed to evaluate deformations during deployment as well as structural performance under operational loads. A 1:10 scale prototype was constructed to illustrate how the structure can be divided into printable segments and assembled to form the complete system.
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This thesis explores the upcycling of post-consumer glass waste into functional acoustic panels for architectural applications. Addressing both environmental concerns and indoor acoustic performance, the research investigates the potential of glass foaming and fusing techniques to transform discarded glass, such as soda lime, light bulb glass, and mixed cullet, into porous, sound-absorbing elements suitable for use in the built environment.
The study begins with a comprehensive literature review on glass recycling, classification of glass waste streams, and limitations within current recycling infrastructures, particularly regarding contaminated or mixed glass cullet. The material science behind foam glass production is examined, with a focus on how porosity, pore size distribution, and pore interconnectivity affect acoustic absorption. Kiln-based secondary casting and fusing techniques are also reviewed as accessible, energy-efficient alternatives to primary glass forming processes. In parallel, the acoustic literature is reviewed to understand key performance indicators such as reverberation time, clarity index, and sound absorption coefficient, especially in relation to porous materials. Furthermore, the review introduces the growing use of computational tools in acoustic design, including the use of simulation environments (such as CATT-Acoustic) and parametric optimization workflows (e.g., in Grasshopper), which allow for data-driven decision-making in early-stage material and geometry development.
A series of experimental trials were conducted to evaluate how various glass types respond to foaming, with particular attention paid to their level of contamination. Variables such as foaming agent type (calcium carbonate, eggshells, manganese dioxide), glass composition, particle size, and firing schedule were tested for their influence on pore development and structural integrity. Glass was successfully foamed at 860°C and 790°C. Notably, eggshells showed strong compatibility not only with clean soda lime cullet, but also with more contaminated light bulb glass and mixed cullet, yielding homogeneous pore structures. Re-foaming tests and prototype casting using 3D-printed moulds demonstrated the adaptability and scalability of the method. Selected samples were tested using an impedance tube, confirming their ability to absorb mid- to high-frequency sound, particularly around 1000 Hz, a range critical to both music and speech. The highest absorption coefficients were achieved with soda lime glass; however, the presence of contamination in other glass types did not significantly diminish acoustic performance of the developed material.
To enhance mechanical integrity, fusing trials were conducted to bond the porous layer to a solid glass surface. This was done without compromising the internal pore structure, achieving successful fusion at 705°C for samples made of both light bulb and soda lime glass paired with soda lime float glass.
To evaluate architectural performance, the panels were applied in a digital acoustic simulation of a real-world case study: the 2200 m³ Theatre Hall at TU Delft. The space suffers from excessive early reflections and high clarity index values. Field measurements were used to calibrate a model in CATT-Acoustic, which then informed a parametric optimization process in Grasshopper to determine optimal panel placement. The strategy focused on reducing C80 while preserving reverberation time, maintaining suitability for both rehearsal and performance scenarios. Although improvements in acoustic metrics were modest, they demonstrated that the porous panels successfully reduced problematic reflections without overly damping the space.
Through the integration of material science, real-world measurement, computational acoustics, and parametric design and design optimization, this thesis presents a viable, circular strategy for converting low-value glass waste into functional acoustic components. The findings point to broader potential applications in performance spaces where a nuanced balance between clarity and reverberation is required, offering a solid foundation for further research into sustainable material acoustics. ... Read more