| Résumé |
Toneholes have an important role in the acoustics of woodwind instruments. In the saxophone, the toneholes are surmounted by a key provided with a pad and what musicians and artisans refer as a “resonator”. They are flat disks made of metal or plastic fixed in the middle of the pad and are called with the acoustically neutral term “cover” in the article. In order to understand their role, measurements of the input impedance of a cylinder topped by a key with interchangeable pads (with and without covers) are performed. For closed holes, pads with covers have a low absorption coefficient; for open holes, effects of the covers on the radiation are highlighted when the key is at a small height. An analysis of the vibrations of the pads shows that these effects can be explained by the high mobility of the pads without a cover, which seems to act as a stiffener. Then, the input impedance measurement of an entire saxophone confirms that, when the holes are closed, the effect of a pad without a cover is to increase the damping. The effect on open holes is close to negligible. Finally, measurements in playing situations show that saxophones without covers have higher harmonic spectral centroids and require greater mouth pressure. |
