Vegetal wools for building application: investigation of optimization approaches for the enhancement of low-frequency sound absorption

Bio-based building materials, such as vegetal wools for thermal and acoustic applications, are increasingly used in construction. Indeed, as they store atmospheric carbon dioxide, they have a lower carbon footprint than conventional materials. Despite high-level multi-functional properties, they suffer from poor low-frequency absorption for thin panels (less than 5 cm thick). Therefore, it seems relevant to investigate the optimization possibilities available, including meta-material approaches, and to adapt them to the specificities of vegetal wools, such as a low air resistivity for hemp and flax wools which are our main concern. To meet this challenge, a state-of-the-art is being carried out to identify the optimization methods best suited to the specific characteristics of vegetal wools. This preliminary work is based on the implementation of an initial optimization concept using a multilayer poroelastic material with a perforated resistive layer. The material structure is optimized using analytical modeling to target low frequencies. Experimental verifications are then carried out to determine the sound absorption coefficient of vegetal wools with optimized configurations.