A comparison of string instruments based on wood properties : Biwa vs. cello

概要

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The Satsuma biwa and the cello are compared from the viewpoint of their wood properties. According to the wood classification diagram, the mulberry traditionally used for the biwa is very far from the Western criteria for the resonance woods such as sitka spruce and maple respectively used for the top and back plate of the cello. The structural responses of these instruments are investigated by measuring the driving-point mobility and the transmission mobility of the top plate. The cello is designed to stress the fundamental, while the biwa is constructed to sustain the higher harmonics that are generated by the "sawari" mechanisms applied to the nut and frets. Since the sawari tone yields a reverberating high-frequency emphasis, it is auditorily discriminated from the lower harmonics, which depend on the mode vibrations of the top plate and the bridge. In addition, the camphor-made biwa is compared with the mulberry-made biwa on their structural responses and the resulting sound spectrograms. The camphor wood is not an excellent substitute for the mulberry. Furthermore, the acoustical features of other Asian stringed instruments, where the paulownia and amboyna wood are used, are briefly discussed in relation to the playing style and musical taste.