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Crotales are center-weighted, tuned cymbals that are found in the percussion section of most orchestras. They are arranged like a keyboard in octave sets and are commercially available in two octaves, from C6 to C8. Little information about the physics of crotales has been reported in the literature, despite their having the interesting property of producing a particularly pleasing sound. In this study, the acoustic and vibrational properties of crotales from C6 to C8 are theoretically and experimentally investigated. Interferograms of typical vibrational modes are presented, and the frequencies of the acoustically important modes of crotales are identified and reported. The acoustic spectra of the crotales are compared to theoretical predictions for thin circular plates and annular plates clamped at the center. These models are found to be insufficient for predicting the normal modes of the crotales. An accurate model is developed using finite element analysis, and this model is used to investigate the effects of subtle changes in the magnitude and size of the center mass on the acoustic spectrum. This investigation serves as a basis for suggestions for improvement of the crotales by modifying the center mass. Finally, the physical parameters for a set of clamped annular plates are derived such that the set has similar acoustic properties to a set of crotales, but with more accurate tuning. The validity of these parameters is confirmed using finite element analysis.

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The Journal of the Acoustical Society of America



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