Determining acoustic and mechanical properties of Australian native hardwood species for guitar fretboard production

Abstract

Australian hardwood species have potential in musical instrumentation replacing hardwood species such as Dalbergia latifolia (Indian rosewood- IRW) which is the main species used in guitar fretboard production. In this study, a detailed characterisation was conducted using dynamic and static testing to determine samples’ mechanical strength. Dynamic testing was conducted using non-destructive acoustic testing to record the sound velocity travelling through boards in the longitudinal grain direction. The elastic modulus for the tested samples was also calculated using the dynamic results. Four point bending tests were conducted in accordance with AS/NZS 4063.1 to determine the bending strength (MOR) and stiffness (MOE) to be compared with the dynamic results. The Janka hardness for each of the species was determined for reference in accordance with the Australian testing method developed by J.J. Mack. Species tested had sound radiation characteristics values close to Indian rosewood (IRW) samples tested. The internal friction of Australian samples tested and IRW were low providing indication for future applications of these species to musical instrument manufacture. Sound quality factor and speed of sound determined for tested species were similar to IRW. Mechanical strength and performance of the tested species displayed similar values to the IRW properties; indicating the potential of these species for long-term use in fretboard applications. The MOE and MOR values for Australian hardwood species were dependent on the density; the Queensland walnut (QWL), Kuranda Satin ash (KSA), Hickory ash (HKA) and Red mahogany (RMG) samples had highest mechanical strength values within the range of IRW including the Janka hardness, MOR and MOE values. The work presented here identified four Australian hardwood species with potential for fretboard production. These species will be tested for sound quality and performance prior to fretboard prototyping.