Download Digital simulation of the diode ring modulator for musical applications In this article, a model of the diode ring modulator is developed, which is based on a model from the literature, but modified to suit musical applications. After a brief introduction to analog ring modulation, a substitute circuit for the diode ring modulator is presented and analyzed, leading to a system of ordinary differential equations (ODEs) of first order. The equations are solved by using Euler’s method. The model is compared with a real ring modulator using the same input waveforms, showing a good match between the simulation and the real device.
Download Real-time dissonancizers: Two dissonance-augmenting audio effects We present two simple perceptually motivated audio effects designed to increase the perceived sensory dissonance/roughness (a process we call “dissonancization”) of audio input. The first involves heterodyning multiple bands of the audio signal at different frequencies to break each sinusoid in each band into two sinusoids separated in frequency by the amount that Kameoka and Kuriyagawa [1] predict will produce a maximally dissonant effect. The second attempts to increase the depth of modulation caused by existing beating partials by exponentiating the amplitude envelope within small bands, enhancing the perceived roughness already present in the signal. The first algorithm can produce very dramatic effects even for very consonant inputs, whereas the second tends to produce a more subtle effect. Both algorithms are quite simple to understand and implement and computationally inexpensive enough to be used in real time, but produce perceptually interesting results. The effects can be selectively applied so as to affect only desired frequency ranges, and can be continuously controlled (e.g. in a performance context) to have more or less impact.
Download Physical parameters of an oscillator changed by active control: application to a xylophone bar By applying active control to an oscillator, its modal behaviour changes. This paper makes a comparison between a second order damped harmonic oscillator and a xylophone bar’s mode. Then it proposes a method for acting on an eigen resonance of a xylophone bar. The purpose is to get sound modifications, by bringing under quantitative and independent control its pitch and its duration. Thus it extends our previous work [1], by using a digital feedback controller.
Download Automated rhythmic transformation of musical audio Time-scale transformations of audio signals have traditionally relied exclusively upon manipulations of tempo. We present a novel technique for automatic mixing and synchronization between two musical signals. In this transformation, the original signal assumes the tempo, meter, and rhythmic structure of the model signal, while the extracted downbeats and salient intra-measure infrastructure of the original are maintained.
Download An augmented reality audio headset Augmented reality audio (ARA) means mixing the natural sound environment with artificially created sound scenes. This requires that the perception of natural environment has to be preserved as well as possible, unless some modification to it is desired. A basic ARA headset consists of binaural microphones, an amplifier/mixer, and earphones feeding sound to the ear canals. All these components more or less change the perceived sound scene. In this paper we describe an ARA headset, equalization of its response, and particularly the results of a usability study. The usability was tested by subjects wearing the headset for relatively long periods in different environments of their everyday-life conditions. The goal was to find out what works well and what are the problems in lengthened use. It was found that acoustically the headset worked fine in most occasions when equalized individually or generically (averaged over several subjects). The main problems of usage were related to handling inconveniences and special environments.
Download Identifying function-specific prosodic cues for non-speech user interface sound design This study explores the potential of utilising certain prosodic qualities of function-specific vocal expressions in order to design effective non-speech user interface sounds. In an empirical setting, utterances with four context-situated communicative functions were produced by 20 participants. Time series of fundamental frequency (F0 ) and intensity were extracted from the utterances and analysed statistically. The results show that individual communicative functions have distinct prosodic characteristics that can be statistically modelled. By using the model, certain function-specific prosodic cues can be identified and, in turn, imitated in the design of communicative interface sounds for the corresponding communicative functions in human-computer interaction.
Download Detection and identification of sparse audio tampering using distributed source coding and compressive sensing techniques In most practical applications, for the sake of information integrity not only it is useful to detect whether a multimedia content has been modified or not, but also to identify which kind of attack has been carried out. In the case of audio streams, for example, it may be useful to localize the tamper in the time and/or frequency domain. In this paper we devise a hash-based tampering detection and localization system exploiting compressive sensing principles. The multimedia content provider produces a small hash signature using a limited number of random projections of a time-frequency representation of the original audio stream. At the content user side, the hash signature is used to estimate the distortion between the original and the received stream and, provided that the tamper is sufficiently sparse or sparsifiable in some orthonormal basis expansion or redundant dictionary (e.g. DCT or wavelet), to identify the time-frequency portion of the stream that has been manipulated. In order to keep the hash length small, the algorithm exploits distributed source coding techniques.
Download Dispersion modulation using allpass filters 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.
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 On the numerical solution of the 2D wave equation with compact FDTD schemes This paper discusses compact-stencil nite difference time domain (FDTD) schemes for approximating the 2D wave equation in the context of digital audio. Stability, accuracy, and efciency are investigated and new ways of viewing and interpreting the results are discussed. It is shown that if a tight accuracy constraint is applied, implicit schemes outperform explicit schemes. The paper also discusses the relevance to digital waveguide mesh modelling, and highlights the optimally efcient explicit scheme.