Acoustics of mallet percussion instruments

Abstract

Mallet percussion instruments generally employ tuned bars with free ends as sound sources. These bars vibrate in many modes, emitting overtones which are generally not harmonic of the fundamental, thus giving mallet percussion instruments their distinctive timbres. Glockenspiel or orchestra bells employ rectangular steel bars, and striking them with hard mallets excites both flexural and torsional modes. Xylophone bars, of rosewood or epoxy, are commonly shaped so that the first overtone is a musical twelfth above the fundamental. Bars of marimbas and vibes, in the low and midrange, have their first overtone tuned two octaves above the fundamental. Marimbas, xylophones, and ribes are usually fitted with tubular resonators which increase the efficiency of sound radiation at the fundamental frequency. Chimes or tubular bells are designed to ring with a bell-like timbre. Triangles, because of their many audible overtones, are usually characterized as having an indefinite pitch. Modes of vibration and sound spectra of each of these instruments are discussed in detail.