Modes of vibration of a sheng reed

The sheng is an Asian mouth organ consisting of a number of bamboo pipes enclosed in a wind chamber with brass free reeds at the end of each pipe inside the chamber. The reed in each pipe typically includes a small wax tuning weight near the free end of the reed tongue. The determination of modes of vibration of these reeds, especially how the tuning weight changes those modes of vibration, is the topic of this paper. Recent research has investigated the acoustics of sheng pipes and compared the measured impedance of sheng pipes augmented with pipe resonators with a theoretical model. This research employs finite element analysis software to construct a theoretical model of sheng reeds and compare that model with measured vibrational analysis data gathered with a laser vibrometer. The primary emphasis is on how well the predicted resonance frequencies compare with measured resonance frequencies of the reed as indicated in a response curve. Also compared are the predicted nodal and antinodal positions along the length of the reed with the measured nodal positions. [Research supported by National Science Foundation REU grant PHY-1004860.]