Sound absorption properties of charcoal made from wood waste

Abstract

Wood is a sustainable renewable material that is widely used in the building sector. Due to recent trends in green initiatives in European and other countries, wood waste is becoming more popular for sound absorption and insulation because of its renewability. Recycled wood material granulated charcoal is an effective acoustic treatment. In this study, we investigated the sound absorption coefficients of raw wood and granulated charcoal species: birch (Betula pendula), pine (Pinus sylvestris), and oak (Quercus robur). The impedance tube method was used to characterize the sound absorption properties of the granulated charcoal. The maximum bulk densities of the materials investigated were 567 kg/m3 for birch (B. pendula) wood and 247 kg/m3 for granulated charcoal. The airflow resistivity of wood and granulated charcoal was found using the static airflow method according to the standard. The grain size distribution of charcoal was also determined, with the highest percentage (25–29%) of the birch and pine grain distribution of charcoal species having a size of 400 µm and 30.7% of the oak a size of 1 mm. All species had the lowest grain size value, i.e., 900 µm (1–4%). The sound absorption of granulated charcoal does not depend on the carbonization temperature at 400, 500, or 600 °C. Granular charcoal of 25 mm has a better sound absorption thickness coefficient for birch at 600 °C (0.57 at 315 Hz) compared to wood of the same thickness. The effectiveness of absorption for wood and granular charcoal depends on the type of wood (birch > pine > oak), grain size, airflow resistivity, and bulk density.