Overtone spectra of gongs used in music therapy

Fast Fourier Transform (FFT) study of gong sound spectrograms was carried out on four gongs manufactured by Paiste Company, Switzerland. The results show complex spectra, presented in detail in the present work, that explain the extraordinary sound of the gongs. Each gong has its unique spectrum and its unique time-decay characteristics. The overtone series of the gongs include consonant and dissonant intervals, and have no relation to the harmonic overtone series of musical tones. The theory of an ideal circular membrane was applied in computation of the overtone spectrum of one gong ("World" gong), leading to very good agreement between computed and measured data. Comparison of gongs to other percussions is discussed, and, in particular, a comparison is made with spectra of church bells, vibraphone, and Tibetan singing bowl. The overtone series of the various gongs were found to provide satisfactory explanation to the effect of the gongs on patients subjected to music therapy with gongs. In addition, a special case history of an effect of certain percussion sounds, of interest to music therapy, is described and interpreted with the help of results of FFT analysis.