Observations of non-standard vibrational modes in accordion reeds

Previous studies have found that when an accordion reed is excited by blowing, its frequency spectrum is dominated by transverse modes with torsional modes observed at relatively low amplitudes. In addition, unusual mode shapes and abnormally high amplitude of certain transverse modes have been observed at high pressure. In this research, mode shapes were measured by mechanically driving the reed at the mode frequency, and then plotting velocity amplitude versus position on the reed tongue. The shapes of torsional modes were measured for several of the reeds studied. In addition, a mode that appears to be a fixed-hinged mode was observed in some low-frequency reeds which had a weight on the end. This fixed-hinged mode was first observed when the reed was blown at a relatively high pressure, and then measured by exciting the reed at the same frequency. Odd behavior has also been observed for a number of accordion reeds when they are blown at higher than normal pressure. Observations of these interesting modes will be presented in this talk. [Funded by NSF grant MPS-PHY-REU-2349118.]