Fundamental study on sound absorption characteristics of materials using spherical cellulose beads

Cellulose is the most abundant biomass produced and accumulated on Earth, and it is expected to be used as an alternative to plastic in various industries. One such product is spherical cellulose beads, granular materials made from wood pulp that are biodegradable in soil and seawater. These are used as carriers for fragrances and functional drugs, and cosmetic raw materials. In this study, the authors investigate the potential of spherical cellulose particles as sound absorbing materials using the EA method, an in-situ sound absorption measurement method that can be easily applied at the material development stage. When spherical cellulose beads are used as an acoustic absorber, it may be enclosed in bags or other containers for convenience. First, spherical cellulose beads put in an acrylic case are measured using the EA method under conditions where the particle size or material thickness varied, and their basic characteristics are clarified. Next, sound absorption measurements were performed using the EA method under two conditions: with spherical cellulose beads placed in a bag and without a bag. The results were compared with the acoustic absorption characteristics obtained by the reverberation room method. Finally, reverberation characteristics of a room with the material are measured to show the effect of the absorption characteristics of the material.