自動演奏ベルの振動音響特性に関する研究

概要

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An automatically performing bell system, which informed the specified time with music, has many types of bell configuration and arrangement. The first requirement for the bell system is to tune the fundamental resonance frequencies of each bell to an equal temperament of scale. Finite Element Method (FEM) was used to determine the natural frequency of the bell and the effect of bell profile such as thickness and diameter on the natural frequencies was analyzed. Experimental evaluation was also carried out to examine the natural frequencies and mode shapes of the similar profile bell series and constant thickness bell series. The tuning algorithm of the fundamental and higher mode frequencies by changing the inner profile of the bell to improve the sound quality was developed using FEM successive calculation and its availability was discussed. Moreover, the acoustic radiation properties of the vibrating bell were examined by use of the Boundary Element Method.