Download Modeling Interactions between Rubbed Dry Surfaces Using an Elasto-Plastic Friction Model 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.
Download Self-Sustained Vibrating Structures Physical Modelling by Means of Mass-Interaction Networks GENESIS is a sound synthesis and musical creation environment based on the mass-interaction CORDIS-ANIMA physical modelling formalism. It has got the noteworthy property that it allows to work both on sound itself and on musical composition in a single coherent environment. In this paper we present the first results of a study that is carried out with GENESIS on a particular type of models: self-sustained oscillating structures. By trying to build physical models of real instruments like bowed strings or woodwinds, our aim is to develop and analyse generic tools that can be used for the production of self-sustained oscillations on every mass-interaction network built with GENESIS. But, if the family of the self-sustained oscillating structures is very interesting to create rich timbres, it can also play a new and fundamental role at the level of the temporal macrostructure of the music (that of the gesture and the instrumental performance, as well as the composition). Indeed, it is possible, as we will propose in this paper, to use the relatively complex motion of a bowed macrostructure in a musical composition way, as a musical events generator.
Download Distortion and Pitch Processing Using a Modal Reverberator Architecture A reverberator based on a room response modal analysis is adapted to produce distortion, pitch and time manipulation effects, as well as gated and iterated reverberation. The so-called “modal reverberator” is a parallel collection of resonant filters, with resonance frequencies and dampings tuned to the modal frequencies and decay times of the space or object being simulated. Here, the resonant filters are implemented as cascades of heterodyning, smoothing, and modulation steps, forming a type of analysis/synthesis architecture. By applying memoryless nonlinearities to the modulating sinusoids, distortion effects are produced, including distortion without intermodulation products. By using different frequencies for the heterodyning and associated modulation operations, pitch manipulation effects are generated, including pitch shifting and spectral “inversion.” By resampling the smoothing filter output, the signal time axis is stretched without introducing pitch changes. As these effects are integrated into a reverberator architecture, reverberation controls such as decay time can be used produce novel effects having some of the sonic characteristics of reverberation.
Download Passive Admittance Matrix Modeling for Guitar Synthesis In physics-based sound synthesis, it is generally possible to incorporate a mechanical or acoustical immittance (admittance or impedance) in the form of a digital filter. Examples include modeling of the termination of a string or a tube. However, when digital filters are fitted to measured immittance data, care has to be taken that the resulting filter corresponds to a passive mechanical or acoustical system, otherwise the stability of the instrument model is at risk. In previous work, we have presented a simple method for designing and realizing inherently passive scalar admittances, by composing the admittance as a linear combination of positive real (PR) functions with nonnegative weights. In this paper the method is extended to multidimensional admittances (admittance matrices). The admittance matrix is synthesized as a sum of PR scalar transfer functions (second-order filters) multiplied by positive semidefinite matrices. For wave-based modeling, such as digital waveguides (DWGs) or wave digital filters (WDFs), the admittance matrix is converted to a reflectance filter. The filter structure is retained during conversion, resulting in a numerically robust implementation. As an example, a dual-polarization guitar string model based on the DWG approach is connected to the reflectance model parameterized from guitar bridge admittance measurements.
Download A Virtual Tube Delay Effect A virtual tube delay effect based on the real-time simulation of acoustic wave propagation in a garden hose is presented. The paper describes the acoustic measurements conducted and the analysis of the sound propagation in long narrow tubes. The obtained impulse responses are used to design delay lines and digital filters, which simulate the propagation delay, losses, and reflections from the end of the tube which may be open, closed, or acoustically attenuated. A study on the reflection caused by a finite-length tube is described. The resulting system consists of a digital waveguide model and produces delay effects having a realistic low-pass filtering. A stereo delay effect plugin in P URE DATA1 has been implemented and it is described here.
Download Score based real-time performance with a virtual violin This paper describes the implementation of a violin physical model tied with the control of music scores to enable the real-time performance of music pieces. The violin model is made of four strings, which allows the performance of double stops, chords and specific resonant effects that can be encountered in violin playing. A graphic tablet is used to control the bowing parameters and to trigger automatically note events contained in a specifically formatted MIDI file. The automatic pitch change helps reducing the violin playing complexity and enables the user to focus on sound shaping and phrasing. The device can be used for pure sound synthesis purposes as well as for experiments related to violinists’ sound control. However, the simplified interface for sound and score events is particularly suitable for non violinists wishing to explore expressive capabilities of the instrument and to experience specific features of violin playing.
Download A Numerical Scheme for Various Nonlinear Forces, Including Collisions, Which Does Not Require an Iterative Root Finder Nonlinear forces are ubiquitous in physical systems, and of prominent importance in musical acoustics. Though many models exist to describe such forces, in most cases the associated numerical schemes rely on iterative root finding methods, such as NewtonRaphson or gradient descent, which are computationally expensive and which therefore could represent a computational bottleneck. In this paper, a model for a large class of nonlinear forces is presented, and a novel family of energy-conserving finite difference schemes given. The schemes only require the evaluation of the roots of a quadratic function. A few applications in the lumped case are shown, and the robustness and accuracy of the scheme tested.
Download Non-Iterative Solvers For Nonlinear Problems: The Case of Collisions Nonlinearity is a key feature in musical instruments and electronic circuits alike, and thus in simulation, for the purposes of physics-based modeling and virtual analog emulation, the numerical solution of nonlinear differential equations is unavoidable. Ensuring numerical stability is thus a major consideration. In general, one may construct implicit schemes using well-known discretisation methods such as the trapezoid rule, requiring computationally-costly iterative solvers at each time step. Here, a novel family of provably numerically stable time-stepping schemes is presented, avoiding the need for iterative solvers, and thus of greatly reduced computational cost. An application to the case of the collision interaction in musical instrument modeling is detailed.
Download Sound morphologies due to non-linear interactions : towards a perceptive control of environmental sound-synthesis processes This paper is concerned with perceptual control strategies for physical modeling synthesis of vibrating resonant objects colliding nonlinearly with rigid obstacles. For this purpose, we investigate sound morphologies from samples synthesized using physical modeling for non-linear interactions. As a starting point, we study the effect of linear and non-linear springs and collisions on a single-degreeof-freedom system and on a stiff strings. We then synthesize realistic sounds of a stiff string colliding with a rigid obstacle. Numerical simulations allowed the definition of specific signal patterns characterizing the non linear behavior of the interaction according to the attributes of the obstacle. Finally, a global description of the sound morphology associated with this type of interaction is proposed. This study constitutes a first step towards further perceptual investigations geared towards the development of intuitive synthesis controls.