Study of Ivory Alternatives for Koto Bridges: Correlation between Sensory Evaluation and Amplitude Modulation of Fundamental Spectrum

摘要

The bridges of a koto, a Japanese musical instrument, have traditionally been made of ivory for its superior sound quality and appearance. On the contrary, in the conference of CITES CoP17, 2016, a resolution for the closedown of the domestic market of the ivory was adopted. Therefore, the demand for substitute materials for the ivory is expected to increase in future. Despite this, from the viewpoint of sound quality, the currently available substitute materials used to manufacture koto bridges remain inferior in comparison with ivory. This study investigates the performance of substitute materials by investigating the properties of koto bridges made of metal, resin, and wood. A sensory evaluation of a single tone played by professional and expert koto players was performed for all substitute materials. Additionally, a wavelet analysis of the recorded tone was conducted. The amplitude modulation of the fundamental spectrum level varied in time with respect to each of the chosen materials. The study also includes an investigation of the correlation between sensory evaluation and the recorded amplitude modulation of fundamental spectrum.