Beat wave method for mode pair extraction of a bell type structure

초록

This paper presents a mode pair extraction method for a bell-type structure that employs a generated beat response signal. Due to the occurrence of small asymmetries in the bell structure, a mode pair can be observed on the circumference. Each mode in the pair has very close frequencies and interference between these frequencies produces beats. Beats are a very interesting acoustics phenomenon in the bell sound. Controlling the beat characteristics requires extraction of a mode pair after the bell is cast. The conventional modal test needed excitation force and response signals at several points. On the contrary, the proposed method requires only the beat response measured at two points on the circumference. This method applied the theory of shell-of-revolution and measured the amplitude ratios of the beat wave's peak and the valley. The position of the nodes and anti-nodes of the mode pair was determined using the amplitude ratio and the auto-spectrum. The validity of the new method was verified by comparing the experimental results with those of the multi-point test method. Moreover, this method is much simpler and faster than the conventional ones. (C) 2019 Elsevier Ltd. All rights reserved.

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