Structural and acoustic properties of African padouk (Pterocarpus soyauxii) wood for xylophones

The possibility of supplementing the subjective traditional assessment of wood quality for percussion instruments with reliable acoustic measurements was studied. Sawn boards of African padouk (Pterocarpus soyauxii Taub.) were selected in a timber yard and classified into five grades by using the dynamic combined specific modulus of elasticity. Then they were sawn into raw xylophone bars, which were afterwards traditionally graded by listening to the sound damping at flexural bending excitation and additionally by acoustic measurements. A high quality grade matching of xylophone bars and sawn boards was confirmed. Highly graded material was mostly quarter sawn with straight or moderately interlocked grain. The sound quality of raw xylophone bars was not influenced by the wood density. It negatively correlated with sound damping (tan δ) and positively with the specific modulus of elasticity and with absolute and relative acoustic conversion efficiency. The audial grading of xylophone bars could be improved or substituted by relative acoustic conversion efficiency.

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