Reed chamber resonances in free reed instruments

Abstract

Western free reed instruments such as the accordion, harmonica, and harmonium do not normally employ pipe resonators to determine the pitch, but all do feature some sort of reed chamber or cavity in which the reed is mounted. The reed chamber will necessarily have resonances which can affect the tone quality and the pitch, but, since the cavity volumes are small and the resonances have high frequencies, the effects on the reed vibration generally tend to be small. In some cases, however, a resonance of the reed chamber can be close to the vibration frequency of the reed tongue. In this case, the cavity air vibration can become large enough to influence the self-excitation mechanism, possibly interfering with tongue vibration and the resulting musical tone, and in some cases preventing the sounding of the reed at all. For various configurations of the reed chamber, reed motion during the initial transient stage of free reed vibration has been analyzed, exploring effects on the rise time and final amplitude of vibration due to changes in reed chamber configurations. [Work partially supported by United States National Science Foundation Grant PHY-1004860.]