Explicit Mapping of Acoustic Regimes For Wind Instruments

This paper proposes a methodology to map the various acoustic regimes of wind instruments. The maps can be generated in a multi-dimensional space consisting of design, control parameters, and initial conditions. The bound- aries of the maps are obtained explicitly in terms of the parameters using a support vector machine (SVM) classifier as well as a dedicated adaptive sam- pling scheme. The approach is demonstrated on a simplified clarinet model for which several maps are generated based on different criteria. Examples of computation of the probability of occurrence of a specific acoustic regime are also provided. In addition, the approach is demonstrated on a design optimization example for optimal intonation

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

Regime change thresholds in flute-like instruments: influence of the mouth pressure dynamics

Since they correspond to a jump from a given note to another one, the mouth pressure thresholds leading to regime changes are particularly important quantities in flute-like instruments. In this paper, a comparison of such thresholds between an artificial mouth, an experienced flutist and a non player is provided. It highlights the ability of the experienced player to considerabily shift regime change thresholds, and thus to enlarge its control in terms of nuances and spectrum. Based on recent works on other wind instruments and on the theory of dynamic bifurcations, the hypothe- sis is tested experimentally and numerically that the dynamics of the blowing pressure influences regime change thresholds. The results highlight the strong influence of this parameter on thresholds, suggesting its wide use by experienced musicians. Starting from these observations and from an analysis of a physical model of flute-like instruments, involving numerical continuation methods and Floquet stability analysis, a phenomenological modelling of regime change is proposed and validated. It allows to predict the regime change thresholds in the dynamic case, in which time variations of the blowing pressure are taken into account

Oscillation regimes produced by an alto saxophone: Influence of the control parameters and the bore inharmonicity

International audienceThe aim of this work is to highlight experimentally how inharmonicity of the bore resonance frequencies of an alto saxophone influence the nature of the oscillation regimes. A variable volume branching from the neck of an alto sax at an appropriate position allows to change the frequency of the first resonance independently from the second. A blowing machine with artificial lips is used to make the saxophone play while controlling independently the control parameters : the blowing pressure and an embouchure parameter. Values of these parameters are estimated experimentally through the measurement of the nonlinear characteristics linking the mean air flow blown into the instrument to the static pressure difference across the reed. Experiments with different values of the control parameters as well as of the inharmonicity produce different kinds of oscillation regimes. These regimes are categorized through the analysis of the pressure signal inside the mouthpiece. The resulting maps demonstrate that the emergence of quasi-periodic regimes, and their extent, depend on the level of inharmonicity, but also on the values of the control parameters. Periodic regimes playable by choosing appropriate values of the control parameters also differ according to the level of inharmonicity, a higher inharmonicity facilitating the emergence of the third register

Is the jet-drive flute model able to produce modulated sounds like Flautas de Chinos ?

Flautas de chinos - prehispanic chilean flutes played during ritual celebrations in central Chile - are known to produce very particular beating sounds, the so-called sonido rajado. Some previous works have focused on the spectral analysis of these sounds, and on the input impedance of the complex resonator. However, the beating sounds origin remains to be investigated. Throughout this paper, a comparison is provided between the characteristics of both the sound produced by flautas de chinos and a synthesis sound obtained through time-domain simulation of the jet-drive model for flute-like instruments. Jet-drive model appears to be able to produce quasiperiodic sounds similar to sonido rajado. Finally, the analysis of the system dynamics through numerical continuation methods allows to explore the production mechanism of these quasiperiodic regimes.Comment: Stockholm Music Acoustics Conference, Stockholm : Sweden (2013

Analyse expérimentale de l'effet de l'inharmonicité des instruments a anche simple -Cas du saxophone alto

National audiencePour les instruments de musiquè a vent, l'inharmonicité des fréquences de résonance est une des grandeurs considérées , en facture instrumentale, comme représentatives de la qualité d'un instrument. L'inharmonicité peut altérer le timbre ainsi que la justesse de l'instrument. Pour les saxophones, l'inharmonicité des fréquences de résonances est principalement causée par la troncature de la perce conique ainsi que par la présence des trous latéraux. Le but de ce travail est de mettre en avant expérimentalement l'effet de l'inharmonicité des fréquences de résonances sur la nature des régimes d'oscillation produits par un instrument a anche simple. Un piston est fixé au niveau du bocal d'un saxophone alto afin de diminuer progressivement lapremì ere fréquence de résonance , ce qui permet de modifier l'inharmonicité de l'instrument. Une bouche artificielle est utilisée afin de mettre en oscillation l'instrument avec des param etres de contrôle constants (param etre d'embouchure et pression statique dans la bouche). Ces param etres sont evalués expérimentalement par le biais d'une mesure de la caractéristique non linéaire. Par modification des param etres de contrôle et de l'inharmonicité, une grande diversité de régimes d'oscillation est observée expérimentalement. Ces régimes sont identifiés par l'analyse du signal de pression a l' intérieur du bec. En particulier, des régimes d'oscillation quasi-périodiques sont produits sous forme de sons multiphoniques

Seuils d'oscillation de la clarinette : validité de la représentation excitateur-résonateur

National audienceDepuis Helmholtz, le fonctionnement des instruments entretenus est représenté par un système bouclé faisant apparaître un bloc excitateur et un bloc résonateur. Dans le cas de la clarinette étudiée ici, l'excitateur désigne l'anche modulant le débit d'air entrant et le résonateur le corps de l'instrument. Si cette représentation est communément admise, se pose la question de la séparabilité de ces deux blocs et de l'observabilité des grandeurs physiques qui les lient. Dans le cadre de l'étude du seuil d'oscillation, nous inspectons la validité de cette représentation indépendamment de toute modélisation des blocs : les seuils mesurés sont comparés avec ceux obtenus par la théorie des oscillateurs dans laquelle sont introduites les valeurs expérimentales des paramètres du modèle. Les pressions de seuil et les fréquences émergentes obtenues en (3) et (4) sont comparées. L'interprétation des différences fait intervenir les difficultés d'accéder exactement expérimentalement au point de bifurcation (indépendamment de la qualité du contrôle), la caractérisation expérimentale incomplète du système excitateur (en particulier, le débit d'anche n'est pas mesuré), et les incertitudes qui pèsent sur la mesure d'impédance d'entrée d'une clarinette du fait de la géométrie du bec. Toutefois, l'exploitation directe des mesures permet de s'affranchir d'incertitudes qui seraient introduites par une modélisation paramétrique des éléments excitateur et résonateur

Numerical tools for musical instruments acoustics: analysing nonlinear physical models using continuation of periodic solutions

International audienceWe propose a new approach based on numerical continuation and bifurcation analysis for the study of physical models of instruments that produce self- sustained oscillation. Numerical continuation consists in following how a given solution of a set of equations is modified when one (or several) parameter of these equations are allowed to vary. Several physical models (clarinet, saxophone, and violin) are formulated as nonlinear dynamical systems, whose periodic solutions are directly obtained using the harmonic balance method. This method yields a set of nonlinear algebraic equations. The solution of this system, which represent a periodic solution of the instrument, is then followed using a numerical continuation tool when a control parameter (e.g. the blowing pressure) varies. This approach enables us to compute the whole periodic regime of the instruments, without any additional simplification of the models, thus giving access to characteristics such as playing frequency, sound level, as well as sound spectrum as a functions of the blowing pressure

Oscillation thresholds for "striking outwards" reeds coupled to a resonator

International audienceThis paper considers a "striking outwards" reed coupled to a resonator. This expression, due to Helmholtz, is not discussed here : it corresponds to the most common model of a lip-type valve, when the valve is assumed to be a one degree of freedom oscillator. The presented work is an extension of the works done by Wilson and Beavers (1974), Tarnopolsky (2000). The range of the playing frequencies is investigated. The first results are analytical : when no losses are present in the resonator, it is proven that the ratio between the threshold frequency and the reed resonance frequency is found to be necessarily within the interval between unity and the square root of 3. This is a musical sixth. Actually the interval is largely smaller, and this is in accordance with e.g. the results by Cullen et al.. The smallest blowing pressure is found to be directly related to the quality factor of the reed. Numerical results confirm these statements, and are discussed in comparison with previous ones by Cullen et al (2000)