Acoustic and viscoelastic properties of string instrument fretboards made of radiata pine by densification and impregnation with furfuryl alcohol resin

In this study, radiata pine wood was impregnated with furfuryl alcohol (FA) resin and radially compressed at compression ratios (CRs) of 17%, 33%, and 50%, respectively, to improve the acoustic and viscoelastic performance. The optimum CR was selected by analyzing the properties of FA-densified modified woods with different CRs. The storage modulus and loss factors of the FA-densified modified woods with CRs of 17%, 33%, and 50% were better than those of fretboard wood. The fretboard wood had an extremely high dynamic modulus of elasticity (D′\(\ge\) 16.22 GPa) and dynamic shear modulus (G′\(\ge\) 2.23 GPa). The D′ and G′ of the FA-densified modified wood with a CR of 50% were 25.44 GPa and 4.08 GPa, respectively, which are better than those of the fretboard wood. The common fretboard wood had a low sound velocity (υ), small specific dynamic elastic modulus (\({E}_{sp}\)), small sound radiation coefficient (R), and low acoustic conversion efficiency (ACE), along with a high acoustic impedance (ω) and high sound quality factor (Q⁻¹). The values of υ, \({E}_{sp}\), R, ACE, ω, and Q⁻¹ of the FA-densified modified wood with a CR of 50% were 4563 m/s, 19.9 GPa, 3.49 m³ Pa⁻¹ s⁻³, 253, 5.70 10⁶ (Pa s m⁻¹), and 13.80 \(\times\) 10⁻³, respectively, meeting the performance requirements for fretboards and demonstrating the potential to replace fretboard wood in fretboard manufacturing. This research promotes the application of a fast-growing plantation wood for the manufacture of musical instruments and provides a good platform for its high-value utilization.