Low Carbon Sound Absorption
The Development and Acoustic Evaluation of Low Carbon Materials for Noise Mitigation in Infrastructure and Urban Environments
L.P.R. Chabus (TU Delft - Architecture and the Built Environment)
M. Overend – Mentor (TU Delft - Architecture and the Built Environment)
G. Mirra – Mentor (TU Delft - Architecture and the Built Environment)
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Abstract
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.