Reed vibration, pressure, and airflow in Western free-reed instruments

Abstract

Western free reed instruments, including the reed organ, harmonium, harmonica, and accordion, use asymmetric free reeds that are able to maintain sustained oscillation in the absence of a pipe resonator. Studies of the motion of air‐driven American reed organ reeds and accordion reeds have been made that yield the volume air flow through the reed opening as a function of time. Reed vibration waveforms are obtained using a variable impedance transducer, and corresponding sound pressure waveforms are obtained from a probe microphone at positions near the reed opening on both sides of the reed tongue. The airflow waveform is obtained by integrating the pressure waveform and using a calculated area function and is calibrated using the measured average and minimum airflow rates. The results are compared with earlier preliminary studies as well as recent theoretical work. For pressure and airflow waveforms among different types of reeds or for the same reed at different blowing pressures, differences can be understood in terms of the configuration of the reed and reed frame system, as well as the amplitude of reed vibration. [Research supported by NSF REU Grant No. PHY‐0354058.]