Wood anatomy and acoustic properties of selected tropical hardwoods

Abstract

Selected anatomical features and ground tissue composition were studied in four tropical hardwoods (Afzelia sp. [Doussié], Intsia sp. [Merbau], Astronium sp. [Muiracatiara] and Millettia sp. [Wengé]). These woods can be applied in musical instrument production, especially for xylophone bars. The measured density, 1st bending natural frequency and the logarithmic decrement of damping were used to calculate other acoustic properties such as dynamic young modulus of elasticity (Erf), specific modulus of elasticity (E´/ρ), internal friction (tan δ), and acoustic conversion efficiency (ACE). The correlations between anatomy and acoustic properties were determined. Despite difficulties in specifying general characteristics of hardwoods due to their complicated and variable structure, correlations valid between species were found for specific modulus of elasticity. Specific modulus of elasticity was negatively correlated with ray tissue volume and positively with ray height to width ratio and fiber length. The diversity in ground tissue composition was the main criterion for the species choice and probably should condition diverse correlations of anatomical features found for individual species. It seems that better acoustic properties (higher stiffness, ACE or specific modulus of elasticity) are performed by wood with longer fibers and slender rays, causing minimal deflection of adjoining fibers.