Broadband sound absorption via Algal biofoams and Helmholtz resonator arrays

The construction industry is responsible for a large percentage of the global greenhouse gas emissions, material consumption, and waste. The industry is undergoing a process of material replacement to counteract this trend, replacing high carbon and resource intensive materials such as plastics, metals, and concrete, with renewable and biodegradable materials coming from plants. Sound absorptive foams, traditionally derived from plastics, are no exception. This work presents the design, fabrication, and analysis of resonant absorbers with algal foam layers and linings, with the objective of efficient broadband absorption and a reduction of our environmental impact. Different species of algae are lyophilized to create biofoams of different densities and structural properties. The sound absorption coefficient and acoustic impedance of these samples are measured with the impedance tube method, and these properties are then used to create analytical and FEM models of the proposed absorptive panels. These models, in combination with stochastic optimization algorithms, are used to generate the geometry of the Helmholtz cavities that best make use of the biofoam to enhance the viscothermal losses and impedance matching. The study aims to make use of the large design freedom present in Helmholtz resonator geometry to generate designs tailored to the algae.