Paper Archive

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.

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In this paper, a model for the interaction of the strings with the frets in a guitar or other fretted string instruments is introduced. In the two-polarization representation of the string oscillations it is observed that the string interacts with the fret in different ways. While the vertical oscillation is governed by perfect or imperfect clamping of the string on the fret, the horizontal oscillation is subject to friction of the string over the surface of the fret. The proposed model allows, in particular, for the accurate evaluation of the elongation of the string in the two modes, which gives rise to audible dynamic detuning. The realization of this model into a structurally passive system for use in digital waveguide synthesis is detailed. By changing the friction parameters, the model can be employed in fretless instruments too, where the string directly interacts with the neck surface.

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In physical modelling synthesis, articulation and tuning are effected via time-variation in one or more parameters. Adopting hammered strings as a test case, this paper develops extended forms of such control, proposing a numerical formulation that affords online adjustment of each of its scaled-form parameters, including those featuring in the one-sided power law for modelling hammerstring collisions. Starting from a modally-expanded representation of the string, an explicit scheme is constructed based on quadratising the contact energy. Compared to the case of time-invariant contact parameters, updating the scheme’s state variables relies on the evaluation of two additional analytic partial derivatives of the auxiliary variable. A numerical energy balance is derived and the numerical contact force is shown to be strictly non-adhesive. Example results with time-variant tension and time-variant contact stiffness are detailed, and real-time viability is demonstrated.

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This paper presents a hybrid reverberation processor, i.e. a realtime audio signal processing unit that combines a convolution reverb for recreating the early reflections of a measured impulse response (IR) with a feedback delay network (FDN) for synthesizing the reverberation tail. The FDN is automatically adjusted so as to match the energy decay profile of the measured IR. Particular attention is given to the transition between the convolution section and the FDN in order to avoid audible artifacts. The proposed reverberation processor offers both computational efficiency and flexible perceptual control over the reverberation effect.

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Acceleration of audio workloads on generally-programmable GPU (GPGPU) hardware offers potentially high speedup factors, but also presents challenges in terms of development and deployment. We can increasingly depend on such hardware being available in users’ systems, yet few real-time audio products use this resource. We propose a suite of benchmarks to qualify a GPU as suitable for batch or real-time audio processing. This includes both microbenchmarks and higher-level audio domain benchmarks. We choose metrics based on application, paying particularly close attention to latency tail distribution. We propose an extension to the benchmark framework to more accurately simulate the real-world request pattern and performance requirements when running in a digital audio workstation. We run these benchmarks on two common consumer-level platforms: a PC desktop with a recent midrange discrete GPU and a Macintosh desktop with unified CPUGPU memory architecture.

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Sound control by gesture is a peculiar topic in Human-Computer Interaction: many different approaches to it are available, focusing each time on diversified perspectives. Our point of view is an interdisciplinary one: taking into account technical considerations about control theory and sound processing, we try to explore the expressiveness world which is closer to psychology theories. Starting from a state of the art which outlines two main approaches to the problem of ”making sound with gestures”, we will delve into psychological theories about expressiveness, describing in particular possible applications dealing with intermodality and mixed reality environments related to the Gestalt Theory. HCI design can indeed benefit from this kind of approach because of the quantitative methods that can be applied to measure expressiveness. Interfaces can be used in order to convey expressiveness, which is a plus of information that can help interacting with the machine; this kind of information can be coded as spatio-temporal schemes, as it is stated in Gestalt theory.

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The image method is generalized to geometries with an arbitrary number of spatial dimensions. n-dimensional (n-D) acoustics is discussed, and an algorithm for n-D room impulse response calculations is presented. Synthesized room impulse responses (RIRs) from n-D rooms are presented. RIR characteristics are discussed, and computational considerations are examined.

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For physical modelling sound synthesis, many techniques are available; time-stepping methods (e.g., finite-difference time-domain (FDTD) methods) have an advantage of flexibility and generality in terms of the type of systems they can model. These methods do, however, lack the capability of easily handling smooth parameter changes while retaining optimal simulation quality and stability, something other techniques are better suited for. In this paper, we propose an efficient method to smoothly add and remove grid points from a FDTD simulation under sub-audio rate parameter variations. This allows for dynamic parameter changes in physical models of musical instruments. An instrument such as the trombone can now be modelled using FDTD methods, as well as physically impossible instruments where parameters such as e.g. material density or its geometry can be made time-varying. Results show that the method does not produce (visible) artifacts and stability analysis is ongoing.

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This paper proposes the sonification of the activity of a computer system that allows the user to monitor the basic performance parameters of the system, like CPU load, read and write activity of the hard disk or network traffic. Although, current computer systems still produce acoustic background noise, future and emerging computer systems will be more and more optimized with respect to their noise emission. In contrast to most of the concepts of auditory feedback, which present a particular sound as a feedback to a user’s command, the proposed feedback is mediated by the running computer system. The user’s interaction stimulates the system and hence the resulting feedback offers more realistic information about the current states of performance of the system. On the one hand the proposed sonification can mimic the acoustical behavior of operating components inside a computer system, while on the other hand, new qualities can be synthesized that enrich interaction with the device. Different forms of sound effects and generation for the proposed auditory feedback are realized to experiment with the usage in an environment of silent computer systems.

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Nonlinear interactions between different parts of musical instruments present several challenges regarding the formulation of reliable and efficient numerical sound synthesis models. This paper focuses on a numerical collision model that incorporates impact damping. The proposed energy-based approach involves an iterative solver for the solution of the nonlinear system equations. In order to ensure the efficiency of the presented algorithm a bound is derived for the maximum number of iterations required for convergence. Numerical results demonstrate energy conservation as well as convergence within a small number of iterations, which is usually much lower than the predicted bound. Finally, an application to music acoustics, involving a clarinet simulation, shows that including a loss mechanism during collisions may have a significant effect on sound production.

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