| Résumé |
The accordion is a free-reed instrument. The two identical reeds associated with one note are driven separately by the airflow created by the inward and outward movements of the bellow. In this present study, attention is focused on understanding the aerodynamic phenomena involved in reed vibration. The acoustical model is deduced from the variation of the flow rate through the slot in the reed plate. A variety of laboratory measurements and observations on different accordion reeds have been made with defferent blowing pressures. Among them : near-field sound pressure (microphones above and under the reed); displacement and velocity of the reed (capacitive sensor and laser vibrometer system); reed profile, magnified stroboscopic images, flow visualization; etc. From these experimental results, we have extracted the most important phenomena involved, which are to be implemented in a physical model accurate enough to describe the behavior of the reed and to reproduce its characteristic sound. This physical model must be as simple as possible to be computationally efficient and usable in sound synthesis. For example, at Ircam, it is possible to program the accordion model in Modalys, a synthesizer language based on modal representation formalism. Similarities and differences between simulated and real sounds will be discussed.
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