Acoustics of a Chinese hand-exercise ball
Edward R. Mansell, Thomas D. Rossing · The Journal of the Acoustical Society of America · 1993
Pairs of steel balls, 3–4 cm in diameter, have been used in China as hand exercisers since the time of the Ming dynasty. Often a sounding device, consisting of a coil spring and a small steel ball, is placed inside the balls to produce a rather delicate tinkling sound as the balls are moved in circles in the hand. It is claimed that the balls can produce sounds ‘‘which are like the whistling of a dragon and singing of a phoenix.’’ The sound spectrum shows many strong partials up to 10 kHz or higher. The most identifiable pitch of G5 results from a partial at 773 Hz.