Comparison between methods to characterize the acoustical properties of musical toneholes
Abstract
In woodwind instruments, lateral holes or toneholes, are used to reduce the effective length of the instrument in order to increase the number of notes that can be played. Over the time, instrument makers have noticed that details of the tonehole's geometry play a major role in the musical quality of woodwind instruments, a change in geometry impacts parameters such as: tuning, volume, and timbre. From the scientific point of view, it is of interest to link the tonehole's geometry to the acoustical properties of the produced sound. A single tonehole can be represented by a lumped T circuit comprised of a shunt and series impedance. In order to determine the values of these impedances, several methods have been developped, [Keefe 1982, Nederveen 1998, Dubos et al. 1999, Dalmont et al. 2002, Dickens 2007, Lefebvre and Scavone 2012], these include theoretical, experimental, and numerical approaches. In this study a new method is proposed and compared to the method developed by Dalmont et al. (2002). The new approach is based on two measurements of the input impedance instead of the measurement of the input and transfer impedances of the methodology proposed by Dalmont et al. Also the tonehole position does not need to be at the middle of the main tube. Simulations of the experiments of both methologies were performed to compare the effect of the uncertainty over the accuracy of the results. These results can be used for the design, and improvement of woodwind instruments.
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