The natural variability of spruce soundboards: Perceptual differences in the in the tonal quality of acoustic guitars

Abstract

The wood of the spruce tree (Picea spp.) has been valued for centuries as an ideal soundboard for stringed instruments, due to its material acoustic properties. There is large variability in these properties between individual trees of the same species, and even within an individual log. It stands to reason that this variability would produce audible differences in sound quality in otherwise identical musical instruments. Further, there may be a specific combination of material properties of the soundboard that would result in optimal sound quality for a given design, as measured by expert listeners. Nine steel string guitars of the same model were produced by the Taylor Guitar Company, with strict control of all production parameters. The guitars varied only in two parameters: the density and the Young's modulus of the soundboard and bracewood. A short music sequence was used for pairwise comparisons in a double-blind listening test. The results suggest that, for this particular model (the Taylor 814ce Grand Auditorium), low density and Young's modulus of the soundboard and bracewood have a positive impact on overall preference. More generally, these results underscore the importance of integrating a given design with the physical characteristics of the component wood.