Prediction of the dynamic oscillation threshold in a clarinet model with a linearly increasing blowing pressure : influence of noise

This paper presents an analysis of the effects of noise and precision on a simplified model of the clarinet driven by a variable control parameter. When the control parameter is varied the clarinet model undergoes a dynamic bifurcation. A consequence of this is the phenomenon of bifurcation delay: the bifurcation point is shifted from the static oscillation threshold to an higher value called dynamic oscillation threshold. In a previous work [8], the dynamic oscillation threshold is obtained analytically. In the present article, the sensitivity of the dynamic threshold on precision is analyzed as a stochastic variable introduced in the model. A new theoretical expression is given for the dynamic thresholds in presence of the stochastic variable, providing a fair prediction of the thresholds found in finite-precision simulations. These dynamic thresholds are found to depend on the increase rate and are independent on the initial value of the parameter, both in simulations and in theory.Comment: 14 page

SCIENTIFIC CONCERTS OR LEARNING ACOUSTICS WITH ARTS

International audienceThis paper presents the concept of "scientific concerts" developed at Le Mans University by two acoustics teachers-researchers and professional musicians, with the collaboration of three professional musicians. This project was born in 2009 and aims to introduce the basic concepts of acoustics by mixing science and arts. The originality and core principle of a scientific concert is to combine projected animations and spoken explanations with real-time experiments and demonstrations that are being given and played by both physicists and musicians. Learning is also eased by alternating musical themes and scientific content. Two different shows have been developed and given either in high schools, in popular science events or in concerts halls welcoming teenagers or general audience. The first show deals with the three main characteristics of a sound (intensity, pitch, timbre), while the second introduces the physics of musical instruments using the principles of elemental resonators like ducts and strings. The presentation will describe the science-to-music back-and-forth process that has been followed so as to achieve this project, including examples of experiments and auditory demonstrations. A quantitative and qualitative assessment of the concerts given in France and Canada will be finally provided

Objective and subjective characterization of saxophone reeds

The subjective quality of single cane reeds used for saxophone or clarinet may be very different from a reed to another although reeds present the same shape and the same strength. In this work, we propose to compare three approaches for the characterization of reeds properties. The first approach consists in measuring the reed mechanical response ("in vitro" measurement) by means of a specific bench which gives equivalent dynamic parameters (mass, damping, stiffness) of the first vibration mode. The second approach deals with the measurement of playing parameters "in vivo", using specific sensors mounted on the instrument mouthpiece. These measurements provide specific parameters in playing condition, such as the threshold pressure or the spectral centroid of the sounds. Finally, subjective tests are performed with a musician in order to assess the reeds according to subjective criteria, characteristic of the perceived quality. Different reeds chosen for their subjective differences (rather difficult and dark, medium, rather easy and bright) are characterized by the three methods. First results show that correlations can be established between "in vivo" measurements and subjective assessments

EXPERIMENTAL CHARACTERISATIONS OF SINGLE CANE REEDS

International audienceSingle cane reeds used for playing clarinets or saxophones are described by makers by their strength and shapes (cutting). For reeds assumed to be identical according to the maker (same strength and shape), strong differences in the perceived quality are expressed by musicians. In this context, the experimental characterization of reeds (from the perceptive and objective sides) is a key issue for reed makers in order to better predict reed musical abilities. This paper presents and discuss different measurement methods. These methods can be divided into two families, measurement of the reed alone through static or dynamic measurements in order to derive stiffness and modal parameters, measurement of the "embouchure" (reed+mouthpiece+lip) alone through static or quasi-static measurements in order to estimate the non linear characteristics, the non linear reed stiffness or other mechanical parameters. Finally it appears that the most efficient characterisation of the "embouchure" is probably a static measurement

Prediction of the dynamic oscillation threshold in a clarinet model with a linearly increasing blowing pressure

14 pagesInternational audienceReed instruments are modeled as self-sustained oscillators driven by the pressure inside the mouth of the musician. A set of nonlinear equations connects the control parameters (mouth pressure, lip force) to the system output, hereby considered as the mouthpiece pressure. Clarinets can then be studied as dynamical systems, their steady behavior being dictated uniquely by the values of the control parameters. Considering the resonator as a lossless straight cylinder is a dramatic yet common simplification that allows for simulations using nonlinear iterative maps. In this paper, we investigate analytically the effect of a time-varying blowing pressure on the behavior of this simplified clarinet model. When the control parameter varies, results from the so-called dynamic bifurcation theory are required to properly analyze the system. This study highlights the phenomenon of bifurcation delay and defines a new quantity, the dynamic oscillation threshold. A theoretical estimation of the dynamic oscillation threshold is proposed and compared with numerical simulations

Prediction of the dynamic oscillation threshold of a clarinet model: comparison between analytical predictions and simulation results

International audienceSimple models of clarinet instruments based on iterated maps have been used in the past to successfully estimate the threshold of oscillation of this instrument as a function of a constant blowing pressure. However, when the blowing pressure gradually increases through time, the oscillations appear at a much higher value than what is predicted in the static case. This is known as bifurcation delay, a phenomenon studied in [1] for a clarinet model. In numerical simulations the bifurcation delay showed a strong sensitivity to numerical precision

Insertion d'informations numériques dans un signal : Application à la classification de données expérimentales en anémométrie laser Doppler

Ce travail propose d'évaluer une procédure de marquage de signaux expérimentaux en anémométrie laser à effet Doppler. La méthode adoptée est basée sur une technique d'étalement de spectre et des mesures de corrélation. L'impact du marquage sur la qualité des estimations des paramètres de la vitesse particulaire acoustique est mesuré de manière objective à l'aide d'une méthode basée sur la dérivée de la phase du signal

Analysis of Nonlinear Characteristics of the Clarinet Exciter Obtained via a New Measurement Method

International audienceA new method for measuring the nonlinear characteristic of the clarinet exciter, which binds the air flow entering into the clarinet with the pressure drop (∆p) across the reed, is described. It uses a clarinet mouthpiece equipped with a reed and an artificial lip whose position ψ is controlled by a micrometer screw. The mouthpiece is connected to a bottle in which a moderate vacuum is generated at the beginning of the experiment. After a short time lapse, the opening of the reed occurs. The ther-modynamics of the volume in isochoric conditions enables the calculation of the volume velocity entering the mouthpiece from the pressure measurement. 13 reeds with 10 different embouchures are measured. The measurements enabled the estimation of the equivalent aeraulic section S(∆p, ψ). We propose a model of S as a convex function of ∆p and ψ, defined as the sum of two 1D stiffening springs plus a porosity constant. The mean standard error of the model is 0.2%

Response of an artificially blown clarinet to different blowing pressure profiles

Using an artificial mouth with an accurate pressure control, the onset of the pressure oscillations inside the mouthpiece of a simplified clarinet is studied experimentally. Two time profiles are used for the blowing pressure: in a first set of experiments the pressure is increased at constant rates, then decreased at the same rate. In a second set of experiments the pressure rises at a constant rate and is then kept constant for an arbitrary period of time. In both cases the experiments are repeated for different increase rates. Numerical simulations using a simplified clarinet model blown with a constantly increasing mouth pressure are compared to the oscillating pressure obtained inside the mouthpiece. Both show that the beginning of the oscillations appears at a higher pressure values than the theoretical static threshold pressure, a manifestation of bifurcation delay. Experiments performed using an interrupted increase in mouth pressure show that the beginning of the oscillation occurs close to the stop in the increase of the pressure. Experimental results also highlight that the speed of the onset transient of the sound is roughly the same, independently of the duration of the increase phase of the blowing pressure.Comment: 14 page