Download Higher-Order Scattering Delay Networksfor Artificial Reverberation Computer simulations of room acoustics suffer from an efficiency vs accuracy trade-off, with highly accurate wave-based models being highly computationally expensive, and delay-network-based models lacking in physical accuracy. The Scattering Delay Network (SDN) is a highly efficient recursive structure that renders first order reflections exactly while approximating higher order ones. With the purpose of improving the accuracy of SDNs, in this paper, several variations on SDNs are investigated, including appropriate node placement for exact modeling of higher order reflections, redesigned scattering matrices for physically-motivated scattering, and pruned network connections for reduced computational complexity. The results of these variations are compared to state-of-the-art geometric acoustic models for different shoebox room simulations. Objective measures (Normalized Echo Densities (NEDs) and Energy Decay Curves (EDCs)) showed a close match between the proposed methods and the references. A formal listening test was carried out to evaluate differences in perceived naturalness of the synthesized Room Impulse Responses. Results show that increasing SDNs’ order and adding directional scattering in a fully-connected network improves perceived naturalness, and higher-order pruned networks give similar performance at a much lower computational cost.
Download Interaction-optimized Sound Database Representation Interactive navigation within geometric, feature-based database representations allows expressive musical performances and installations. Once mapped to the feature space, the user’s position in a physical interaction setup (e.g. a multitouch tablet) can be used to select elements or trigger audio events. Hence physical displacements are directly connected to the evolution of sonic characteristics — a property we call analytic sound–control correspondence. However, automatically computed representations have a complex geometry which is unlikely to fit the interaction setup optimally. After a review of related work, we present a physical model-based algorithm that redistributes the representation within a user-defined region according to a user-defined density. The algorithm is designed to preserve the analytic sound-control correspondence property as much as possible, and uses a physical analogy between the triangulated database representation and a truss structure. After preliminary pre-uniformisation steps, internal repulsive forces help to spread points across the whole region until a target density is reached. We measure the algorithm performance relative to its ability to produce representations corresponding to user-specified features and to preserve analytic sound–control correspondence during a standard density-uniformisation task. Quantitative measures and visual evaluation outline the excellent performances of the algorithm, as well as the interest of the pre-uniformisation steps.
Download Simulation of piano sustain-pedal effect by parallel second-order filters This paper presents a sustain-pedal effect simulation algorithm for piano synthesis, by using parallel second-order filters. A robust two-step filter design procedure, based on frequency-zooming ARMA modeling and least squares fit, is applied to calibrate the algorithm from impulse responses of the soundboard and the string register. The model takes into account the differences in coupling between the various strings. The algorithm can be applied to both sample-based and physics-based piano synthesizers.
Download A perceptually inspired generative model of rigid-body contact sounds Contact between rigid-body objects produces a diversity of impact and friction sounds. These sounds can be synthesized with detailed simulations of the motion, vibration and sound radiation of the objects, but such synthesis is computationally expensive and prohibitively slow for many applications. Moreover, detailed physical simulations may not be necessary for perceptually compelling synthesis; humans infer ecologically relevant causes of sound, such as material categories, but not with arbitrary precision. We present a generative model of impact sounds which summarizes the effect of physical variables on acoustic features via statistical distributions fit to empirical measurements of object acoustics. Perceptual experiments show that sampling from these distributions allows efficient synthesis of realistic impact and scraping sounds that convey material, mass, and motion.
Download Estimation and Modeling of Pinna-Related Transfer Functions This paper considers the problem of modeling pinna-related transfer functions (PRTFs) for 3-D sound rendering. Following a structural modus operandi, we present an algorithm for the decomposition of PRTFs into ear resonances and frequency notches due to reflections over pinna cavities. Such an approach allows to control the evolution of each physical phenomenon separately through the design of two distinct filter blocks during PRTF synthesis. The resulting model is suitable for future integration into a structural head-related transfer function model, and for parametrization over anthropometrical measurements of a wide range of subjects.
Download Comparison of Germanium Bipolar Junction Transistor Models for Real-time Circuit Simulation The Ebers-Moll model has been widely used to represent Bipolar Junction Transistors (BJTs) in Virtual Analogue (VA) circuits. An investigation into the validity of this model is presented in which the Ebers-Moll model is compared to BJT models of higher complexity, introducing the Gummel-Poon model to the VA field. A comparison is performed using two complementary approaches: on fit to measurements taken directly from BJTs, and on application to physical circuit models. Targeted parameter extraction strategies are proposed for each model. There are two case studies, both famous vintage guitar effects featuring germanium BJTs. Results demonstrate the effects of incorporating additional complexity into the component model, weighing the trade-off between differences in the output and computational cost.
Download Physically-based synthesis of nonlinear circular membranes This paper investigates the properties of a recently proposed physical model of nonlinear tension modulation effects in a struck circular membrane. The model simulates dynamic variations of tension (and consequently of partial frequencies) due to membrane stretching during oscillation, and is based on a more general theory of geometric nonlinearities in elastic plates. The ability of the nonlinear membrane model to simulate real-world acoustic phenomena is assessed here through resynthesis of recorded membrane (rototom) sounds. The effects of air loading and tension modulation in the recorded sounds are analyzed, and model parameters for resynthesis are consequently estimated. The example reported in the paper show that the model is able to accurately simulate the analyzed rototom sounds.
Download A Proposal for using SMS for Expression Modeling Spectral models have proven to be a successful method for analyzing and re-synthesizing natural and acoustic sounds, to the extent that a musical phrase can also be modeled in order to extract performance parameters. This paper suggests various parameters which are embedded in the spectral analysis or .sms file and proposes some methods which can be used for expression modeling based upon compositional, perceptive, and cognition approaches. The focus is on achieving the means to construct a translation algorithm which the composer can use as a tool to analyze expressive material such as a musical phrase or a spoken sentence of text, and apply detected parameters to the vectors of a physical model or a synthesis algorithm..
Download A Spatial Interface for Audio and Music Production In an effort to find a better suited interface for musical performance, a novel approach has been discovered and developed. At the heart of this approach is the concept of physical interaction with sound in space, where sound processing occurs at various 3D locations and sending sound signals from one area to another is based on physical models of sound propagation. The control is based on a gestural vocabulary that is familiar to users, involving natural spatial interaction such as translating, rotating, and pointing in 3-D. This research presents a framework to deal with realtime control of 3-D audio, and describes how to construct audio scenes to accomplish various musical tasks. The generality and effectiveness of this approach has enabled us to re-implement several conventional applications, with the benefit of a substantially more powerful interface, and has further led to the conceptualization of several novel applications.
Download Energy and Accuracy Issues in Numerical Simulations of a Non-linear Impact model A physically-based impact model – already known and exploited in the field of sound synthesis – is studied using both analytical tools and numerical simulations. It is shown that, for some regions of the parameter space, the trajectories of discretized systems may drift from analytically-derived curves. Some methods, based on enforcing numerical energy consistency, are suggested to improve the accuracy and stability of discrete-time systems.