Vibrational modes of accordion reeds.

Abstract

Some new measurements made of the oscillation of air-driven accordion reeds show that higher transverse modes through the fourth mode are present as well as the first torsional mode. The second and third transverse modes are observable even at low amplitudes of oscillation. All of these have been previously observed in reed organ reeds [Paquette et al., J. Acoust. Soc. Am. 114, 2348 (2003)]. Additionally, for the first time a lateral mode of vibration (transverse vibration perpendicular to the usual first transverse mode) has been observed. For airflow in a given direction, only one of the two reeds mounted in each wind chamber is the primary source of sound production, but the vibration of the secondary reed has also been studied. The amplitudes of higher-frequency modes relative to the fundamental are observed to be higher in the secondary reed than in the primary reed. Finite element calculations of the reed modes have been made, and the calculated mode frequencies and node locations were used to verify mode identification. [Work partially supported by National Science Foundation REU Grant No. PHY-0354058.]