Modifying the radiation ratio of tonewoods through wood degradation

Abstract

This work investigates different wood modification techniques to modify the acoustical properties of tonewoods, in particular the sound radiation ratio (R). The treatments used were heat- and fungal exposure, as well as immersion into NaOH and Na₂SO₃ solution and a combination of the most successful treatments. All initial experiments were performed on pine (Pinus patula) due to cost factors, before replicating the best performing treatment on high quality spruce tonewood (Picea abies). The main objective was to reduce the hemicellulose content without severely degrading cellulose, which results in a reduction of density, while maintaining, or even improving the elasticity (MOE_L), which results in an increase of R. Overall, the combined heat-fungal and heat-sodium treatments performed best and increased R by up to 20%. Sodium treatment led to the best increases in R, but compromised the wood structure in spruce and the treatment protocol needs to be developed further. Consequently, the most successful wood treatment to improve acoustical properties was determined to be exposure to white rot combined with heat treatment.