Paper Archive

The authors present a collaborative effort on establishing an online course in DSP eartraining. The paper reports from a preliminary workshop that covered a large range of topics such as eartraining in music education, terminology for sound characterization, e-learning, automated tutoring, DSP techniques, music examples and audio programming. An initial design of the web application is presented as a rich content database with flexible views to allow customized online presentations. Technical risks have already been mitigated through prototyping.

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MultiBin is a new tool for binaural audition of multiple sound sources in a user definable environment. Although designed to be flexible in its application, its primary function is to provide dynamic multi-channel binaural simulation. It is built upon two new Csound binaural reverberation opcodes. An early reflection opcode, based on an image source method and a Head-Related Transfer Function interpolation algorithm previously introduced by the authors provides dynamic source and listener location. This is complemented by a later reverberation opcode which provides a diffuse reverb based on a parametric Feedback Delay Network model which considers interaural coherence.

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This paper will consider wave (amplitude) and phase signal shaping techniques for the digital emulation of distortion effect processing. We examine how to determine the Wave- and Phaseshaping functions with harmonic amplitude and phase data. Three distortion effects units are used to provide test data. The action of the Wave- and Phase- shaping functions derived for these effects is demonstrated with the assistance of a superresolution frequency-domain analysis technique.

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Object-oriented programming (OOP) has been for many years now one of the most important programming paradigms used in a variety of applications. Digital audio signal processing can benefit largely from this approach for systems development. In this paper a number of approaches to using object-orientation in audio processing systems are reviewed. Existing systems of audio processing are introduced and discussed in detail. The paper also draws attention to the different OOP techniques enabled and supported by these systems. Comparative code and tutorial examples are included, providing an insight into the development of signal processing applications using objects.

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This text looks at the computer instrument development work and its influence on the composition process. As a preamble to the main discussion, the different types of software for sound generation and transformation are reviewed. The concept of meta-themes is introduced and explored in the context of contemporary music. Two examples of the author’s computer music work are used to discuss the complex relationship between software development and composition. The first piece provides an example of such relationships in the context of ‘tape’ music. The second explores the use of computer instruments in live electroacoustic music. The activities of composition and instrument creation will be shown to be at times indistinguishable and mutually dependent.

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New approaches to Head Related Transfer Function (HRTF) based artificial spatialisation of audio are presented and discussed in this paper. A brief summary of the topic of audio spatialisation and HRTF interpolation is offered, followed by an appraisal of the existing minimum phase HRTF interpolation method. Novel alternatives are then suggested which essentially approach the problem of phase interpolation more directly. The first technique, based on magnitude interpolation and phase truncation, aims to use the empirical HRTFs without the need for complex data preparation or manipulation, while minimizing any approximations that may be introduced by data transformations. A second approach augments a functionally based phase model with low frequency non-linear frequency scaling based on the empirical HRTFs, allowing a more accurate phase representation of the more relevant lower frequency end of the spectrum. This more complex approach is deconstructed from an implementation point of view. Testing of both algorithms is then presented, which highlights their success, and favorable performance over minimum phase plus delay methods.

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This paper introduces a spectral model for plucked, steel string tones, based on functional models for time-varying fundamental frequency and inharmonicity coefficient. Techniques to evaluate those analytical values at different time indexes are reviewed and commented. A method to evaluate the unknowns of the fundamental frequency and inharmonicity coefficient functions and match the data of a given tone is presented. Frequency tracks can thereafter be deployed and traced for all values of time. Their accuracy is discussed, and applications for the model are suggested.

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This paper describes the implementation of a streaming spectral processing system for realtime audio in a consumer-level onboard GPU (Graphics Processing Unit) attached to an off-the-shelf laptop computer. It explores the implementation of four processes: standard phase vocoder analysis and synthesis, additive synthesis and the sliding phase vocoder. These were developed under the CUDA development environment as plugins for the Csound 6 audio programming language. Following a detailed exposition of the GPU code, results of performance tests are discussed for each algorithm. They demonstrate that such a system is capable of realtime audio, even under the restrictions imposed by a limited GPU capability.

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