## 4 Discussion and Conclusions
Compared to packed Ecovative material (\(\alpha=0.28\)) [8], the printed samples showed comparable sound absorption coefficient values across all of the frequency bands. Beyond absorption coefficient values, using the proposed fabrication method in this study provides the ability to produce lower-density acoustic panels with reduced material used, and the potential to fabricate complex, customized geometries. The fabricated acoustic panels have potential applications in interior architecture (e.g., wall panels, ceiling baffles, partitions), noise control in public spaces (e.g., libraries, offices, auditoriums, educational facilities), and bio-integrated urban design aiming for sustainable acoustic solutions. The acoustic performance in this study is measured using an impedance tube, which offers frequency-dependent sound absorption data. While this method is established for empirical assessment of the sample, it does not offer data about the microstructural characteristics that control the sound propagation within the material. Mycelium-based composites are porous materials with an interconnected hyphal network and interconnected voids formed during the fungal growth [33], allowing for air permeability and visco-thermal dissipation of sound. Among the microstructural modeling approaches to characterize the acoustic behavior of porous materials, the Johnson-Champoux-Allard (JCA) model offers a physically grounded method for predicting acoustic properties of the material based on measurable microstructural parameters, including open porosity, air-flow resistivity, tortuosity, viscous characteristic length, and thermal characteristic length [34; 35]. JCA is a model that estimates the bulk density and bulk modulus of porous materials by modeling them as a homogeneous fluid medium [36]. While this model was not used in this study, future investigations could adopt the JCA framework to advance the empirical testing. While this was not within the scope of this study, mechanical performance remains a critical consideration for the architectural application of mycelium-based composites. Future work should address key mechanical properties of the developed material, including compressive strength, dimensional stability, and flexural resistance. Previous studies have laid important groundwork on the mechanical characteristics of mycelium-based composites, though using different substrates or fungi strains than those used in this study. Research has shown that substrate composition, fiber characteristics, and post-processing of the material significantly influence mechanical strength and moisture sensitivity [37; 38]. Reinforcement using bacterial cellulose has been reported to enhance tensile and compressive strength [39], while functional grading with nanoclay improves stiffness and toughness [40]. Other studies have examined the effects of incubation time, natural fiber additives, and substrate blends on compressive and flexural performance [41; 42]. Cultivation factors such as substrate density and growth duration also play a significant role in determining compressive strength, with denser substrates and shorter cultivation periods yielding stronger materials [43]. These findings establish a foundational for future investigations into the mechanical performance of the mycelium-based material developed in this study, particularly in the context of its potential integration into other architectural applications. Contamination during the growth and fabrication process was minimized using sterile tools and a controlled environment. However, this study did not assess contamination risk following the drying phase. Similarly, the biodegradability rate and long-term material behavior under varying humidity and temperature conditions were not examined. A recent study explored the biodegradability of mycelium composites by adapting a soil burial test under controlled conditions, showing that material composition, fabrication method, and environmental factors influence the disintegration process.