Generic resonator models for real-time synthesis of reed and brass instruments

International audienceFrom accurate measurements of bore profiles of various reed and brass instruments, a common and simplified geometrical model made of three parts totalizing seven geometrical parameters is proposed. From this geometry, it is shown that a good approximation of the input impedance can be obtained by a combination of two lumped elements gathered in series and parallel with a distributed element. Each element is approximated and discretized in order to end up with costless digital filters representing the impedance impulse response. These filters require the order of twenty multiplication/additions per sample and their coefficients are analytically expressed as functions of the geometrical parameters. The choice of the geometry and the time discretization schemes are validated both through comparison with continuous models and through the estimation of the geometrical parameters via a global optimization procedure, using measured input impedance curves

Approximation of the acoustic radiation impedance of a cylindrical pipe

Useful approximation formulae for radiation impedance are given for the reflection coefficients of both infinitely flanged and unflanged rigid-walled cylindrical ducts. The expressions guarantee that simple but necessary physical and mathematical principles are met, like hermitian symmetry for the reflection coefficient (identical behaviour of positive and negative frequencies) and causality for the impulse response. A non causal but more accurate expression is also proposed that is suitable for frequency-domain applications. The formulae are obtained by analytical and numerical fitting to reference results from Levine & Schwinger for the unflanged case and extracted from the radiation impedance matrix given by Zorumski for the infinite flanged case.Comment: Journal of Sound and Vibration (2008) accepte

Physics of wind instruments an overview of studies carried out at LMA

International audienceA poster is presented with the aim of doing an overview of the research activities carried out on the physics of wind instruments at the Laboratory of Mechanics and Acoustic

Evaluating the Relationship between Spermatogenic Silencing of the X Chromosome and Evolution of the Y Chromosome in Chimpanzee and Human

Chimpanzees and humans are genetically very similar, with the striking exception of their Y chromosomes, which have diverged tremendously. The male-specific region (MSY), representing the greater part of the Y chromosome, is inherited from father to son in a clonal fashion, with natural selection acting on the MSY as a unit. Positive selection might involve the performance of the MSY in spermatogenesis. Chimpanzees have a highly polygamous mating behavior, so that sperm competition is thought to provide a strong selective force acting on the Y chromosome in the chimpanzee lineage. In consequence of evolution of the heterologous sex chromosomes in mammals, meiotic sex chromosome inactivation (MSCI) results in a transcriptionally silenced XY body in male meiotic prophase, and subsequently also in postmeiotic repression of the sex chromosomes in haploid spermatids. This has evolved to a situation where MSCI has become a prerequisite for spermatogenesis. Here, by analysis of microarray testicular expression data representing a small number of male chimpanzees and men, we obtained information indicating that meiotic and postmeiotic X chromosome silencing might be more effective in chimpanzee than in human spermatogenesis. From this, we suggest that the remarkable reorganization of the chimpanzee Y chromosome, compared to the human Y chromosome, might have an impact on its meiotic interactions with the X chromosome and thereby on X chromosome silencing in spermatogenesis. Further studies will be required to address comparative functional aspects of MSCI in chimpanzee, human, and other placental mammals

Modélisation de signaux sonores par transformées temps-échelle et temps-fréquence

Les représentations énergétiques en temps et échelle, ou en temps et fréquence distribuent l'information contenue dans les modulations du signal en fonction de ces variables. Pour les signaux à modulation linéaire d'amplitude et sinusoïdale en fréquence, ces procédés mettent en évidence le retard de groupe et la fréquence instantanée. Trois procédés d'étude, scalogramrne (ondelette en module carré), représentation de Wigner-Ville et représentation de Unterberger, version passive, permettent d'extraire les paramètres de modulation de signaux rencontrés en acoustique musicale.Energetic time-scale representations or time-frequency representations deal with data related to the signal modulations, with a dependance on the upper variables. For linear amplitude modulations and sinusoidal frequency ones, these tools point out the group delay and the instantaneous frequency. Extraction of modulation parameters on music acoustical signals, is provided by the scalogram (square modulus of the wavelet transform), the Wigner-Ville time-frequency representation and the passive Unterberger time-scale representation

Synthesis Of Musical Sounds:

Musical sounds are produced by vibrating structures. The motion of such structures can be modeled using mechanical equations. Nevertheless, these models are not adapted to the real-time synthesis of sounds. This paper addresses the design of synthesis models for musical sounds, in particular the ones produced by a vibrating string. We describe the relationship between the mechanical model and the synthesis model that must satisfy the hearing