Experimental study of the effects of the long chimney of a closed tonehole on the sound of a bassoon.

The bassoon has side holes a few tens of millimeters long, much longer than in other woodwinds. When they are closed, the "quarter-wave" resonances of these "chimneys" create short circuits in parallel with the bore. At these resonance frequencies, near 2 kHz-within the sensitive range of hearing-it is expected that the waves will not propagate beyond the chimney, affecting both the input impedance and the radiated sound. Using parametric studies with varying chimney lengths, these effects on impedance and radiated sound are measured for a French bassoon and a simplified conical model instrument. The effects are clear on the model instrument, especially when several chimneys have equal length. For the bassoon, the passive filter effect remains, but its importance in the sound is blurred due to changes in the oscillation regime and in the directivity, as simulations confirmed. The effect is audible under laboratory conditions, but on the same order of magnitude as the spatial level variations due to the directivity. It is, therefore, unlikely that the difference in timbre between the French and the German bassoon is mainly due to longer tonehole chimneys.

Woodwind instrument design optimization based on impedance characteristics with geometric constraints.

Computational optimization algorithms coupled with acoustic models of wind instruments provide instrument makers with an opportunity to explore new designs. Specifically, they enable the automatic discovery of geometries exhibiting desired resonance characteristics. In this paper, the design optimization of woodwind instruments with complex geometrical features (e.g., non-cylindrical bore profile and side holes with various radii and chimney heights) is investigated. Optimal geometric designs are searched so that their acoustic input impedance has peaks with specific target frequencies and amplitudes. However, woodwind instruments exhibit complex input impedance whose features, such as resonances, might have non-smooth evolution with respect to design variables, thus hampering gradient-based optimization. For this reason, this paper introduces new formulations of the impedance characteristics (resonance frequencies and amplitudes) using a regularized unwrapped angle of the reflection function. The approach is applied to an illustrative instrument subjected to geometric constraints similar to the ones encountered by manufacturers (a key-less pentatonic clarinet with two-registers). Three optimization problems are considered, demonstrating a strategy to simultaneously adjust several impedance characteristics on all fingerings.

Music in a bag? Controlling the bag of Majorcan and Galician bagpipes.

After defining the mechanical framework of the bag control of bagpipe, this paper presents a study of the bag pressure control in a musical context through the comparison of six players and two bagpipes: one Galician (gaita) and one Majorcan (xeremies), the latter mainly differentiated organologically by a much larger bag size. General observations first lead to the identification and interpretation of the range of control parameters observed. A more detailed analysis of the control parameters during the production of steady notes highlights the coordination between insufflations and the arm displacement necessary to produce a stable and continuous sound. Finally, the bag pressure variation is observed in a musical context and correlated with the musical task, thus, associating different control strategies to the different bagpipes played by the musicians.

Time-domain simulation of flute-like instruments: comparison of jet-drive and discrete-vortex models.

This paper presents two models of sound production in flute-like instruments that allow time-domain simulations. The models are based on different descriptions of the jet flow within the window of the instrument. The jet-drive model depicts the jet by its transverse perturbation that interacts with the labium to produce sound. The discrete-vortex model depicts the jet as two independent shear layers along which vortices are convected and interact with the acoustic field within the window. The limit of validity between both models is usually discussed according to the aspect ratio of the jet W/h, with W the window length and h the flue channel height. The present simulations, compared with experimental data gathered on a recorder, allow to extend the aspect ratio criterion to the notion of dynamic aspect ratio defined as λ/h where λ is the hydrodynamic wavelength that now accounts for geometrical properties, such as W/h, as well as for dynamic properties, such as the Strouhal number. The two models are found to be applicable over neighboring values of geometry and blowing pressure.