Influence of accordion reed chamber geometry on reed vibration and airflow.

Abstract

An experimental study has been made on the motion of air-driven accordion reeds in which some measurements were made with the reed block removed from the instrument, but most were made with the reeds in the instrument with the bellows replaced by a clear acrylic wind chest driven at appropriate blowing pressure by a small organ blower. Measurements of reed displacement and velocity as a function of time were made using a laser vibrometer system, and corresponding sound pressure waveforms were obtained from a probe microphone near the reed opening. Airflow waveforms were calculated by integrating the pressure waveform and using a computed area function. Effects of changes in reed chamber geometry on the reed vibration spectrum and the airflow waveform have been investigated, along with effects on the spectrum of the radiated sound and sounding frequency. Results of changes in the position of the pallet valve, such as partial opening, have also been studied. Additional measurements made for each reed include the variation in sounding frequency and amplitude of vibration with blowing pressure. The results are compared with previous measurements and calculations from theoretical models. [Work partially supported by National Science Foundation REU Grant No. PHY-0354058.]