Influences of the shapes of a temple bell’s parts on acoustic characteristics

The relationships between the various shapes in a Buddhist temple bell and the corresponding acoustic characteristics are clarified mainly by Finite Element Method (FEM) analysis. First, we show that the cross-sectional shapes of the “komazume” (lower part, which is slightly thicker than the rest of the bell) have high correlations to the vibration modes as well as to the vibration positions. As a result, the komazume has a large influence on the bell’s acoustic characteristics. The beat sound is another important factor in the bell’s overall sound, but its origin has not yet been fully clarified. Since the beat sound is assumed to be generated by the bell’s formal or material asymmetrical factors, the influences of a few formal asymmetrical factors on the beat sound are investigated. First, the beat sound obtained by simulation using miniaturized bells is confirmed to closely match the experimental results. Then, it is shown that the “doza” (part where the bell is struck), which functions as a formal asymmetrical factor when the bell vibrates, is highly related to the beat sound. It is also clarified that the “obi” (perpendicular stripe pattern on the bell’s surface) also slightly influences the beat sound.