Paper Archive

In this paper the problem of the synthesis of plucked strings by means of physically inspired models is reconsidered in the context of the player’s interaction with the virtual instrument. While solutions for the synthesis of guitar tones have been proposed, which are excellent from the acoustic point of view, the problem of the control of the physical parameters directly by the player has not received sufficient attention. In this paper we revive a simple model previously presented by Cuzzucoli and Lombardo for the player’s touch. We show that the model is affected by an inconsistency that can be removed by introducing the finger/pick perturbation in a balanced form on the digital waveguide. The results, together with a more comprehensive model of the guitar have been implemented in a VST plugin, which is the starting point for further research.

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Real-time sound synthesis of musical instruments based on solving differential equations is of great interest in Musical Acoustics especially in terms of linking geometry features of musical instruments to sound features. A major restriction of accurate physical models is the computational effort. One could state that the calculation cost is directly linked to the geometrical and material accuracy of a physical model and so to the validity of the results. This work presents a methodology for implementing realtime models of whole instrument geometries modelled with the Finite Differences Method (FDM) on a Field Programmable Gate Array (FPGA), a device capable of massively parallel computations. Examples of three real-time musical instrument implementations are given, a Banjo, a Violin and a Chinese Ruan.

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Latent force models are a Bayesian learning technique that combine physical knowledge with dimensionality reduction — sets of coupled differential equations are modelled via shared dependence on a low-dimensional latent space. Analogously, modal sound synthesis is a technique that links physical knowledge about the vibration of objects to acoustic phenomena that can be observed in data. We apply latent force modelling to sinusoidal models of audio recordings, simultaneously inferring modal synthesis parameters (stiffness and damping) and the excitation or contact force required to reproduce the behaviour of the observed vibrational modes. Exposing this latent excitation function to the user constitutes a controllable synthesis method that runs in real time and enables sound morphing through interpolation of learnt parameters.

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Digital musical instruments based on physical modelling have gained increased popularity over the past years. This is partly due to recent advances in computational power, which allow for their real-time implementation. One of the great potentials for digital musical instruments based on physical models, is that one can go beyond what is physically possible and change properties of the instruments which are static in real life. This paper presents a real-time implementation of the dynamic stiff string using finitedifference time-domain (FDTD) methods. The defining parameters of the string can be varied in real time and change the underlying grid that these methods rely on based on the recently developed dynamic grid method. For most settings, parameter changes are nearly instantaneous and do not cause noticeable artefacts due to changes in the grid. A reliable way to prevent artefacts for all settings is under development.

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Dispersion is a physical phenomenon that makes sound waves more or less inharmonic. Most physical sound synthesis models consider dispersion as a constant property that does not change during the course of a musical event. However, these models would be more expressive without such a restriction. This paper describes a dispersion amount parameter for precise control over inharmonicity, and then experiments with control and audio rate modulation of that parameter. In this research we found that inharmonicity of a plucked string could be smoothly controlled in real-time, and that novel sonic material could be synthesized when the modulation rate was raised into audio range. Instability of the string model with certain parameter values was considered to be problematic.

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We propose different real-time spatial-modal manipulations of a physical model of a singing bowl. The high number of degrees of freedom in the model, combined with spatial processing algorithms, provides the possibility of obtaining rich and expressive transformations.

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In this paper, a flexible strategy to control a synthesis model of sounds produced by non linear friction phenomena is proposed for guidance or musical purposes. It enables to synthesize different types of sounds, such a creaky door, a singing glass or a squeaking wet plate. This approach is based on the action/object paradigm that enables to propose a synthesis strategy using classical linear filtering techniques (source/resonance approach) which provide an efficient implementation. Within this paradigm, a sound can be considered as the result of an action (e.g. impacting, rubbing, ...) on an object (plate, bowl, ...). However, in the case of non linear friction phenomena, simulating the physical coupling between the action and the object with a completely decoupled source/resonance model is a real and relevant challenge. To meet this challenge, we propose to use a synthesis model of the source that is tuned on recorded sounds according to physical and spectral observations. This model enables to synthesize many types of non linear behaviors. A control strategy of the model is then proposed by defining a flexible physically informed mapping between a descriptor, and the non linear synthesis behavior. Finally, potential applications to the remediation of motor diseases are presented. In all sections, video and audio materials are available at the following URL: http://www.lma.cnrs-mrs.fr/~kronland/ thoretDAFx2013/

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Physical modeling sound synthesis for systems in 3D is a computationally intensive undertaking; the number of degrees of freedom is very large, even for systems and spaces of modest physical dimensions. The recent emergence into the mainstream of highly parallel multicore hardware, such as general purpose graphical processing units (GPGPUs) has opened an avenue of approach to synthesis for such systems in a reasonable amount of time, without severe model simplification. In this context, new programming and algorithm design considerations appear, especially the ease with which a given algorithm may be parallelized. To this end finite difference time domain methods operating over regular grids are explored, with regard to an interesting and non-trivial test problem, that of the timpani drum. The timpani is chosen here because its sounding mechanism relies on the coupling between a 2D resonator and a 3D acoustic space (an internal cavity). It is also of large physical dimensions, and thus simulation is of high computational cost. A timpani model is presented, followed by a brief presentation of finite difference time domain methods, followed by a discussion of parallelization on GPGPU, and simulation results.

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I am proposing an event generation system for sonification purposes, where a simplified chain reaction model known as nuclear fission in physics is used. The basic background of the fission model, mapping of parameters as sonic entities and technical aspects of the realization procedure are presented.

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A physically based model of the frictional interaction between dry surfaces is presented. The paper reviews a number of static and dynamic friction models, and discusses numerical techniques for the accurate and efficient numerical implementation of a dynamic elasto-plastic model. An application to the bowed string is provided, and the resulting simulations are compared to recent results from the literature.

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