2001 Volume 22 Issue 3 Pages 209-218
In this paper, we introduce a new percussion instrument, “hokyo,” made of a particular stone, “Sanukite,” and study its vibrational properties. The hokyo has a unique and somewhat complicated structure. Vibrational modes of the hokyo were analyzed by the finite element method, and their existence was verified by fast Fourier analysis of its tone and experimental modal analysis. The vibrational modes of the hokyo are principally determined by the rather simple behavior of the centered inner rod with a quasi-fixed end and a free end. The term “quasi-fixed end” means that the inner rod is not fixed exactly but only approximately at the base. The important modes of the inner rod are the fundamental bending mode, the torsional mode, and the longitudinal mode. The out of phase motion between the inner rod and the outer frame of a hokyo, coupled to each other by the base, produces a quasi-fixed boundary condition at the base. The quasi-fixed end gives a practical advantage to the hokyo in that it can shorten the length of the instrument very much compared to the instrument with free ends.