A Study on Developing Percussion Instrument with Tobe Pottery

The present study is aimed to develop percussion instruments such as wind bell, hand bell, etc. with Tobe pottery which is a traditional product of Ehime prefecture in Japan. Not only the fundamental natural frequency corresponding to the desired music scale is designed, but also the higher order natural frequencies are considered in order to obtain a pleasant sound color. The material properties and vibration characteristics of the Tobe pottery are investigated by impact test and spectral analysis at first. And then, using the finite element method software, the shape of each musical scale model is estimated by changing the sizes of the Tobe pottery numerically. Since the second natural vibration is a major factor influencing the tone color, two approaches are used to change the tone color: (1) optimizing the shape of the pottery so that the second natural frequency changes to an objective frequency under a specified fundamental natural frequency, and (2) optimizing the shape of the pottery so that the contribution ratio of the second vibration changes under a specified fundamental natural frequency. Both approaches are developed with the basis vector method which is a technique of shape optimization. Finally, because of the shrinkage of material after firing, the initial shape of the pottery before the firing is also estimated. Numerical examples are given to show the effectiveness of the proposed approach.