ギター響板用材の音響的性質

抄録

The top plate of guitar is usually made from two wood species which belong to different genus, that is, german spruce (Picea abies) and western redceder (Thuja plicata). To clarify the characteristics of these species and of the wood materials for guitar top plate, the acoustic properties of the specimens prepared from the neighbour portion of the top plate were measured by means of free-free flexural vibration method. The results were compared with the evaluation by an expert of guitar manufacture.
The mean values of specific dynamic Young's modulus (E/γ) and tanδ of german spruce were higher than those of western redceder, while among various wood species these two had higher E/γ and lower tanδ in the longitudinal direction. These characteristics were particularly pronounced in the specimens which were judged by the expert to be high grade. Moreover, the standard deviations of the acoustic properties of the high grade specimens were smaller than those of the medium or low grade ones regardless of the species.
The value of E/γ in the longitudinal direction, which can be obtained easily, seemed to be a convenient criterion for selecting the wood material suitable for guitar top plate. Because it correlated highly with tanδ in the longitudinal direction, and also with the ratio of tanδ in the radial direction to that in the longitudinal direction. Evaluation using both E/γ and tanδ in the longitudinal and radial directions was more appropriate, because the experimental values of E/γ and tanδ in any grain angle agreed with the values calculated based on Hankinson's equation.