Construction and validation of a high resolution finite element model of the Japanese koto

Abstract

The Japanese koto is recognized for its complex resonances, but few studies have been conducted to understand its acoustic properties. This paper presents a COMSOL Multiphysics finite element model of a hand-crafted, professional-grade Japanese koto. To do this, the complex internal and external geometry was captured on 2400 CAT scan cross-sections and imported into Comsol. The model was validated by reference to literature data, Chladni patterns, frequency response experiments, acoustic camera and laser scanning vibrometer studies. These results were then compared to the sound as played on the actual instrument. Challenges in the model’s development arising from the materials and construction of the instrument are discussed, most notably the anisotropic nature of the paulownia wood including multiple grain orientations used in its construction and the added complexity of modeling the organic shape of the real, hand-crafted 1.83 m long instrument with its major internal variations. These developments were guided by parallel studies in less intractable geometry such as simpler box models or models with idealized geometrical shapes lofted along a spline. The CAT scan derived model is used as a quasi-experimental tool to investigate the effect of internal components of the koto on its resonances and results presented.The Japanese koto is recognized for its complex resonances, but few studies have been conducted to understand its acoustic properties. This paper presents a COMSOL Multiphysics finite element model of a hand-crafted, professional-grade Japanese koto. To do this, the complex internal and external geometry was captured on 2400 CAT scan cross-sections and imported into Comsol. The model was validated by reference to literature data, Chladni patterns, frequency response experiments, acoustic camera and laser scanning vibrometer studies. These results were then compared to the sound as played on the actual instrument. Challenges in the model’s development arising from the materials and construction of the instrument are discussed, most notably the anisotropic nature of the paulownia wood including multiple grain orientations used in its construction and the added complexity of modeling the organic shape of the real, hand-crafted 1.83 m long instrument with its major internal variations. These developments were...