Download A 3D Multi-Plate Environment for Sound Synthesis In this paper, a physics-based sound synthesis environment is presented which is composed of several plates, under nonlinear conditions, coupled with the surrounding acoustic field. Equations governing the behaviour of the system are implemented numerically using finite difference time domain methods. The number of plates, their position relative to a 3D computational enclosure and their physical properties can all be specified by the user; simple control parameters allow the musician/composer to play the virtual instrument. Spatialised sound outputs may be sampled from the simulated acoustic field using several channels simultaneously. Implementation details and control strategies for this instrument will be discussed; simulations results and sound examples will be presented.
Download Prepared Piano Sound Synthesis A sound synthesis algorithm which simulates and extends the behaviour of the acoustic prepared piano is presented. The algorithm is based on a finite difference approximation to multiple stiff string vibration, including an excitation method (a hammer) as well as several connected preparation elements, modeled as lumped nonlinearities. Numerical issues and implementation details are discussed, and sound examples are presented.
Download Spring Reverberation: A Physical Perspective Spring-based artificial reverberation was one of the earliest attempts at compact replication of room-like reverberation for studio use. The popularity and unique sound of this effect have given it a status and desirability apart from its original use. Standard methods for modeling analog audio effects are not well suited to modeling spring reverberation, due to the complex and dispersive nature of its mechanical vibration. Therefore, new methods must be examined. A typical impulse responses of a spring used for reverberation is examined, and important perceptual parameters identified. Mathematical models of spring vibration are considered, with the purpose of drawing conclusions relevant to their application in an audio environment. These models are used to produce new results relevant to the design of digital systems for the emulation of spring reverberation units. The numerical solution of these models via the finite difference method is considered. A set of measurements of two typical spring reverberation units are presented.
Download A Coupled Resonant Filter Bank for the Sound Synthesis of Nonlinear Sources This paper is concerned with the design of efficient and controllable filters for sound synthesis purposes, in the context of the generation of sounds radiated by nonlinear sources. These filters are coupled and generate tonal components in an interdependent way, and are intended to emulate realistic perceptually salient effects in musical instruments in an efficient manner. Control of energy transfer between the filters is realized by defining a matrix containing the coupling terms. The generation of prototypical sounds corresponding to nonlinear sources with the filter bank is presented. In particular, examples are proposed to generate sounds corresponding to impacts on thin structures and to the perturbation of the vibration of objects when it collides with an other object. The different sound examples presented in the paper and available for listening on the accompanying site tend to show that a simple control of the input parameters allows to generate sounds whose evocation is coherent, and that the addition of random processes allows to significantly improve the realism of the generated sounds.
Download Real-Time Implementation of an Elasto-Plastic Friction Model using Finite-Difference Schemes The simulation of a bowed string is challenging due to the strongly non-linear relationship between the bow and the string. This relationship can be described through a model of friction. Several friction models in the literature have been proposed, from simple velocity dependent to more accurate ones. Similarly, a highly accurate technique to simulate a stiff string is the use of finitedifference time-domain (FDTD) methods. As these models are generally computationally heavy, implementation in real-time is challenging. This paper presents a real-time implementation of the combination of a complex friction model, namely the elastoplastic friction model, and a stiff string simulated using FDTD methods. We show that it is possible to keep the CPU usage of a single bowed string below 6 percent. For real-time control of the bowed string, the Sensel Morph is used.
Download Numerical Simulation of String/Barrier Collisions: The Fretboard Collisions play a major role in various models of musical instruments; one particularly interesting case is that of the guitar fretboard, the subject of this paper. Here, the string is modelled including effects of tension modulation, and the distributed collision both with the fretboard and individual frets, and including both effects of free string vibration, and under finger-stopped conditions, requiring an additional collision model. In order to handle multiple distributed nonlinearities simultaneously, a finite difference time domain method is developed, with a penalty potential allowing for a convenient model of collision within a Hamiltonian framework, allowing for the construction of stable energy-conserving methods. Implementation details are discussed, and simulation results are presented illustrating a variety of features of such a model.
Download Applications of Port Hamiltonian Methods to Non-Iterative Stable Simulations of the Korg35 and Moog 4-Pole Vcf This paper presents an application of the port Hamiltonian formalism to the nonlinear simulation of the OTA-based Korg35 filter circuit and the Moog 4-pole ladder filter circuit. Lyapunov analysis is
used with their state-space representations to guarantee zero-input
stability over the range of parameters consistent with the actual
circuits. A zero-input stable non-iterative discrete-time scheme
based on a discrete gradient and a change of state variables is
shown along with numerical simulations. Simulations show behavior consistent with the actual operation of the circuits, e.g.,
self-oscillation, and are found to be stable and have lower computational cost compared to iterative methods.
Download Modeling Methods for the Highly Dispersive Slinky Spring: A Novel Musical Toy The ’Slinky’ spring is a popular and beloved toy for many children. Like its smaller relatives, used in spring reverberation units, it can produce interesting sonic behaviors. We explore the behavior of the ’Slinky’ spring via measurement, and discover that its sonic characteristics are notably different to those of smaller springs. We discuss methods of modeling the behavior of a Slinky via the use of finite-difference techniques and digital waveguides. We then apply these models in different structures to build a number of interesting tools for computer-based music production.
Download Modal-Type Synthesis Techniques for Nonlinear Strings with an Energy Conservation Property There has recently been increased interest in the modelling of string vibration under large amplitude conditions, for sound synthesis purposes. A simple nonlinear model is given by the KirchhoffCarrier equation, which can be thought of as a generalization of the wave equation to the case for which the string tension is “modulated” by variations in the length of the string under deformation. Finite difference schemes are one means of approach for the simulation of nonlinear PDE systems; in this case, however, as the nonlinearity is spatially invariant, the solution may be broken down into sinusoidal components, much as in the linear case. More importantly, if time discretization is carried out in a particular way, it is possible to obtain a conserved energy in the numerical scheme, leading to a useful numerical stability guarantee, which can be difficult to obtain for strongly nonlinear systems. Numerical results are presented.