Abstract
So (Koto) is a traditional Japanese horizontal harp; in order to establish a measuring system for quantitatively evaluating the durability of So-strings using So-nails (Koto-zume), the authors developed a measuring apparatus. The durability of three kinds of So-string (silk, multi-polyester, mono-polyester) were determined. The apparatus used a simulated standard So-nail playing method. A So-nail was attached to the shaft of a motor and rotated at a constant speed. The So-nail played the string until it was broken. The authors defined the number of times the string broke as an indicator of the durability of the So-string and developed standard experimental conditions to compare the durability of different strings. The length, tension and play speed were 20cm, 147 N, and 180 rpm respectively. The silk, multi-polyester and mono-polyester strings broke at the times of 3267, 7450 and 11428 times, respectively.
