An investigation of the contribution of a non-linear harmonic to the sound of a Balinese gamelan gong

Balinese gamelan gongs are percussion instruments of special interest because of their unique geometry and sound. Unlike a Chinese tam-tam, the gongs are quite thick, with a protruding dome in the center and long edges that sharply wrap around the circumference of the gong. When struck in the center, the larger gongs are designed to produce a strong beating pattern. Previous studies have shown the cause of this beating phenomenon to be the proximity of the harmonic of the first axis-symmetric mode to the frequency of the second axis-symmetric mode [Krueger et al., J. Acoust. Soc. Am. 128(1) (2010)]. No work has yet been done to characterize this first harmonic in terms of its modal deflection shape or directivity pattern either isolated or coupled with the rest of the system when it produces the beating. This paper will present measurements and discussion of the vibrational and directional characteristics of the gong’s first harmonic as well as the beating system as a whole.