René Caussé

Input impedance of brass musical instruments—Comparison between experiment and numerical models

We present a sequence of measured and calculated input impedance curves for tubes of increasing complexity, culminating in curves for a trombone and for a tuba. Measurements were made by the indirect method in a manner which afforded unprecedented accuracy. Calculations were done with a one‐dimensional model, including visco‐thermal losses, by a method of discretization, employing truncated cones. The correspondence between theory and experiment is sufficiently good that one can use model calculations to predict with some confidence the changes in input impedance caused by modifications to real instruments.

The representation of auditory source characteristics: Simple geometric form

Two experiments examined listeners’ ability to discriminate the geometric shape of simple resonating bodies on the basis of their corresponding auditory attributes. In cross-modal matching tasks, subjects listened to recordings of pairs of metal bars (Experiment 1) or wooden bars (Experiment 2) struck in sequence and then selected a visual depiction of the bar cross sections that correctly represented their relative widths and heights from two opposing pairs presented on a computer screen. Multidimensional scaling solutions derived from matching scores for metal and wooden bars indicated that subjects’ performance varied directly with increasing differences in the width/height (WIH) ratios of both sets of bars. Subsequent acoustic analyses revealed that the frequency components from torsional vibrational modes and the ratios of frequencies of transverse bending modes in the bars correlated strongly with both the bars’ WIH ratios and bar coordinates in the multidimensional configurations. The results suggest that listeners can encode the auditory properties of sound sources by extracting certain invariant physical characteristics of their gross geometric properties from their acoustic behavior.

Sound production in recorderlike instruments. II. A simulation model

A simple one-dimensional representation of recorderlike instruments, that can be used for sound synthesis by physical modeling of flutelike instruments, is presented. This model combines the effects on the sound production by the instrument of the jet oscillations, vortex shedding at the edge of the labium, and turbulence in the mouth of the instrument. The jet oscillation model used is a modification of the semi-empirical model by Fletcher [J. Acoust. Soc. Am. 60, 926–936 (1976)]. The steady-state drive of the acoustical oscillations in the pipe by the jet motion is represented by a pressure jump in the mouth of the instrument. Vortex shedding at the edge of the labium during steady-state operation is taken into account by the use of a free-jet model. The combined effects of this nonlinearity and the jet-drive model enable one to correctly predict the steady-state amplitude of the fundamental. The turbulence noise source is represented by an additional pressure jump across the mouth of the instrument hav...

Bifurcations, Period Doublings and Chaos in Clarinetlike Systems

Wind instruments provide interesting hydrodynamical systems where non-linearities are important but well localized. A simple analysis shows that these systems should undergo Feignebaum-type route to chaos, with a cascade of period doublings. Experiments have been performed fo confirm these predictions

Quasistatic nonlinear characteristics of double-reed instruments

This article proposes a characterization of the double reed in quasistatic regimes. The nonlinear relation between the pressure drop, deltap, in the double reed and the volume flow crossing it, q, is measured for slow variations of these variables. The volume flow is determined from the pressure drop in a diaphragm replacing the instruments bore. Measurements are compared to other experimental results on reed instrument exciters and to physical models, revealing that clarinet, oboe, and bassoon quasistatic behavior relies on similar working principles. Differences in the experimental results are interpreted in terms of pressure recovery due to the conical diffuser role of the downstream part of double-reed mouthpieces (the staple).

Measuring Bow Force in Bowed String Performance : Theory and Implementation of a Bow Force Sensor

A sensor has been developed which allows measurement of the force exerted by the bow on the string ( bow force) during violin performance. The bow force is deduced from measurement of the transvers ...

Elementary stability considerations for bowed‐string motion

Using the approach first pioneered by Raman, the Helmholtz motion of a bowed string is discussed as a special case of “two‐velocity motions,” in which a given point (at which the bow is located) alternates, in the course of a cycle, between two constant velocities. The fact that the bow typically presents a negative resistance to the string during the “slipping” part of the cycle is adduced as a reason for the “duty cycle,” that is, the fraction of the period that corresponds to slipping, to try to become as short as possible. It is shown that, for a string without dissipation or stiffness, this duty cycle can be arbitrarily low for general bow positions; data obtained with the “digital bow” illustrate this behavior. It is shown theoretically, and confirmed with computer simulations, that instabilities arising from the negative slipping resistance cannot be eliminated by assigning a finite positive value to the sticking resistance. The apparent stability of Helmholtz motion observed in real playing situat...

Measurement of acoustic impedance using a capillary: An attempt to achieve optimization

The choice of the dimensions of capillary tubes used for acoustic impedance measurements (with applications to wind musical instruments or materials) depends on the frequency and impedance ranges. It is shown that there is an optimum range for the ratio of the length of the tube to its area, in order to have a flat amplitude response over a wide range of frequency. Several shapes of capillaries, in particular a narrow slit with arbitrary shape, such as a hexagon inscribed in a circle, using an approximate theory of viscothermal effect are studied. The upper limit of frequency does not depend on the shape, but only on the length of the capillary. Therefore, the choice of the dimensions starts with the frequency range, and our study allows one to deduce successively the length, the transverse dimension related to the width of the slit, and finally, from the impedance range, the transverse dimension related to the number of capillaries.

Aerodynamic excitation and sound production of blown-closed free reeds without acoustic coupling: The example of the accordion reed

The accordion reed is an example of a blown-closed free reed. Unlike most oscillating valves in wind musical instruments, self-sustained oscillations occur without acoustic coupling. Flow visualizations and measurements in water show that the flow can be supposed incompressible and potential. A model is developed and the solution is calculated in the time domain. The excitation force is found to be associated with the inertial load of the unsteady flow through the reed gaps. Inertial effect leads to velocity fluctuations in the reed opening and then to an unsteady Bernoulli force. A pressure component generated by the local reciprocal air movement around the reed is added to the modeled aerodynamic excitation pressure. Since the model is two-dimensional, only qualitative comparisons with air flow measurements are possible. The agreement between the simulated pressure waveforms and measured pressure in the very near-field of the reed is reasonable. In addition, an aeroacoustic model using the permeable Ffowcs Williams-Hawkings integral method is presented. The integral expressions of the far-field acoustic pressure are also computed in the time domain. In agreement with experimental data, the sound is found to be dominated by the dipolar source associated by the strong momentum fluctuations of the flow through the reed gaps.

On gestural variation and coarticulation effects in sound control

In this paper we focus on the analysis of sound producing gestures in the musical domain. We investigate the behavior of intraoral pressure exerted by a trumpet performer in the production of single and concatenated notes. Investigation is carried out with functional data analysis techniques. Results show that different variation patterns occur for single note production, which depend on dynamic level, suggesting the hypothesis that two different motor control programs are available. Results from analysis on consecutive notes give evidence that the coarticulation between two gesture curves cannot be modelled by linear superposition, and that local coarticulation is affected by contiguous units.