Identification of the beat characteristics and damping ratios of the Hwacheon World Peace Bell using wavelet transform

摘要

In this paper, a new measurement technique is proposed to identify the beat characteristics and modal damping ratios of a Korean bell in the casting field. The beat response caused by the mutual interference of mode pair with very close doublet frequency is unique feature of the Korean bell and should be accurately measured in order to quantitatively estimate the bell sound. However, the conventional method based on a filtering concept such as the Fourier transform has difficulty in extracting the beat frequencies and modal damping ratios because the method should individually decompose the measured signal into each mode. The aim of this paper is to propose an effective measurement method to identify the beat frequencies, mode pairs and modal damping ratios using the continuous wavelet transform in a real striking condition. The proposed method is verified with the Hwacheon World Peace Bell cast in the year 2008, which is the largest bell in Korea. In the future, the proposed method can be applicable to the casting field of the Korean bell to effectively estimate its beat characteristics and damping characteristics.