Contribution to harmonic balance calculations of self-sustained periodic oscillations with focus on single-reed instruments

International audienceThe harmonic balance method ͑HBM͒ was originally developed for finding periodic solutions of electronical and mechanical systems under a periodic force, but has been adapted to self-sustained musical instruments. Unlike time-domain methods, this frequency-domain method does not capture transients and so is not adapted for sound synthesis. However, its independence of time makes it very useful for studying any periodic solution, whether stable or unstable, without care of particular initial conditions in time. A computer program for solving general problems involving nonlinearly coupled exciter and resonator, HARMBAL, has been developed based on the HBM. The method as well as convergence improvements and continuation facilities are thoroughly presented and discussed in the present paper. Applications of the method are demonstrated, especially on problems with severe difficulties of convergence: the Helmholtz motion ͑square signals͒ of single-reed instruments when no losses are taken into account, the reed being modeled as a simple spring

Remelting of Aluminium by Continuous Submersion of Rolled Scrap

When remelting aluminium scrap, metal losses due to dross generation is a common problem. Reduction of these losses will give substantial economic and environmental benefits. Dross is generated when aluminium metal oxidizes and films of oxide envelope molten metal. When a cold metal object is immersed in a melt, the heat of the melt around this is transferred so rapidly into the object that a shell of melt often solidifies to the surface of the object. When scrap with low bulk density is charged to a melt, solidification of melt on the cold scrap prevents melt from entering the cavities in the bulk of the scrap, and the bulk density remains low. Thus the scrap tends to float on the melt surface. Submersion of this scrap is important to avoid oxidation and subsequent dross generation. One solution to this is to roll scrap to a strip and feed it into the melt. This system has been examined by studying feeding of a continuous, thin aluminium plate into molten aluminium. Also, the effect of lacquer was considered, as well as feeding the plate into a launder with melt flowing along the surface of the plate. An analytical, one-dimensional, steady-state model has been developed to describe the melting and the melting mechanisms. It is based on a shell solidifying on the plate surface and a gap introducing a thermal resistance 1/hg between the shell and the plate. The thermal resistance 1/hl of the boundary layer of the melt is included. Depending on these resistances, the initial temperature of the plate and the melt temperature, a shell will form, and the plate will penetrate a distance P into the melt before it melts away. An experimental apparatus was designed and constructed to feed aluminium plate from a coil into a melt bath at a specified velocity. The plate could be withdrawn rapidly to “freeze” the situation like it was below the melt surface. The penetration depth P of the plate could be measured and shell formation observed. More than 200 experiments were performed, and by comparing the penetration depth at different feeding velocities and melt temperatures to model predictions, the two heat-transfer coefficients hl and hg could be determined by curve fitting. They agree reasonably well with values found in the literature and calculated from boundary-layer theory. In a few experiments, the plate feeding was recorded on video tape, and the cross section of some plates was studied in a microscope. Feeding of somewhat thicker plates was also tried. This gave valuable background information for comparing the experiments to the model. We believe that snap-off of the plate due to low mechanical strength around the melting temperature may affect the measurement of the penetration depth of the plate. Attempts were also made to measure the temperature in the plate by attaching thermocouples to its surface. The obtained temperature profiles in the plate were compared to the model predictions, but the method needs improvement. A criterion for formation of a shell is formulated and tested against experimental observations. Qualitative agreement is achieved. Even if there is no shell formation, it seems that there will be an air film with thermal resistance 1/hg. This indicates that the melting rate will be independent of whether a shell is formed or not. Two additional models with only one heat-transfer coefficient are also developed in order to challenge the main model. From this analysis it is found that the use of two heat-transfer coefficients is necessary to describe the system. The model should be of direct interest when feeding rolled scrap into molten aluminium. Improvement of the model can be attained by reconsidering the assumptions made, but then numerical methods must undoubtedly be applied. These new models should include the snap-off mechanism

Natural transformation of type and nature of the voice for extending vocal repertoire in high-fidelity applications

cote interne IRCAM: Farner09aNone / NoneNational audienceNatural voice transformation will reduce the need for authentic voices in many situations, ranging from vocal services via education and entertainment to artistic applications. Transformation of one voice to correspond to that of another person has been studied for decades but still suffers from limitations that we propose to overcome by an alternative approach. It consists in modifying pitch, spectral envelope, durations etc. in a global way. While it sacrifices the possibility to attain a specific target voice, the approach allows the production of new voices of a high degree of naturalness with different sex and age, modified vocal quality (soft, breathy, and whisper), or another speech style (dullness and eagerness). The transformation of sex and age has been evaluated by a listening test

Timbre variation as an attribute of naturalness in clarinet play

ISBN 3-540-34027-0International audienc

Voice transformation and speech synthesis for video games

cote interne IRCAM: Farner08bInternational audienceVoice and expressivity transformation as well as text-to-speech synthesis with high degree of naturalness are now available. A set of tools permitting a large range of voices to be made from a single voice, whose speech may be produced from text and given a certain expressivity, is proposed. In the context of multiplayer video games, for instance, this technology allows for creation of the speech of non-player characters as well as for transforming the player’s voice into the voice of her character. The technology behind these tools will be presented. A demonstration using cartoon characters will also be provided