Nonlinearities in recorder tone holes: effect of undercutting
Résumé
Early woodwind instruments have small tone holes that are usually undercut. Undercutting consists in rounding off or chamfering the holes edges where they meet the main bore. The consequences on the acoustics can be classified in two categories, which are the linear and the non linear acoustical effects. Linear effects are induced by the modification of the hole geometry, which can be modelled in the linear theory by a cylindrical hole with a larger section and a slight change in position along the bore. It is shown that makers use those modifications as a way of tuning instruments during the last stages of the manufacturing process. The other effect of undercutting is to reduce the kinetic energy loss caused by discontinuities in the vicinity of the hole. Experimental results show the consequences on the recorder, especially modifications of the pressure thresholds of oscillating regimes. Other characteristics of played notes are also studied, such as the spectral centroid or the radiated power.
Domaines
Acoustique [physics.class-ph]
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