Download The Modified Chamberlin and Zölzer Filter Structures
The Chamberlin and Zölzer filter structures run a risk, albeit small, of requiring a large value for one of their tuning coefficients, which may lead to performance issues. A simple modification leads to alternative structures that place an absolute bound on that coefficient while retaining the signal flow topology. The modified structures also affect the pole distribution. In the case of the Chamberlin structure, the changes upon modification can be interpreted as favorable.
Download Smooth and Safe Parameter Interpolation of Biquadratic Filters in Audio Applications
Parameter interpolation (PI) of biquadratic IIR filters (biquads) is widely used in audio applications to avoid very undesirable audible effects like plops, clicks etc. It is shown that although the simplest linear PI of numerator and denominator coefficients of the transfer function of a biquad guarantees the stability it, however, may sometimes lead to other audible side effects caused, for example, by the possible growth of the magnitude response at some frequencies in some intermediate states of PI procedure. To avoid audible transients and to make the PI easily portable into digital signal processor (DSP) a special technique is applied called here “sliding edges”. The detailed description of this technique and their comparison is the goal of the present paper.
Download X-Micks - Interactive Real-Time Content Based Audio Processing
In this article we present the real-time audio plug-in X-Micks, an audio processing application allowing for remixing and hybridization of two beat-synchronized audio streams, which provides user interaction based on the extraction and visual rendering of information from the two real-time audio streams. In the current version, the plug-in uses the beat grid information provided by the plug-in host and a real-time estimation of energy in chosen frequency bands to construct an interactive matrix representation allowing for intuitive and efficient user interaction based on familiar representations such as the sonogram and the step sequencer. After trying to formulate the constitutional qualities of a rising new generation of audio processing tools of which we claim X-Micks being an exemplary specimen, the article gives an overview over the application’s interface, functionalities and implementaion.
Download Dispersion Modeling in Waveguide Piano Synthesis Using Tunable Allpass Filters
This paper extends a previously proposed method for designing filters simulating the dispersion phenomenon occurring in string instruments. In digital waveguide synthesis, the phenomenon is traditionally modeled by inserting an allpass filter to the string model feedback loop. In this paper, the concept of tunable dispersion filter design, which provides a closed-form formula to design a dispersion filter, is applied to a cascade of first-order allpass filters. Moreover, the method is extended to design a filter cascade including an arbitrary number of first-order filters. In addition, it is shown how the designed dispersion filter can be used in a waveguide piano synthesis model.
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 Digital Synthesis Models of Clarinet-Like Instruments Including Nonlinear Losses in the Resonator
This paper presents a real-time algorithm for the synthesis of reed instruments, taking into account nonlinear losses at the first open tonehole. The physical model on which the synthesis model relies on is based on the experimental works of Dalmont et al. who have shown that for high pressure levels within the bore, an air jet obeying the Bernoulli flow model, hence acting as a nonlinear resistance, is created at the open end of the bore. We study the effect of these additional losses on the response of the bore to an acoustic flow impulse at different levels and on the self oscillations. We show that at low frequencies, these nonlinear losses are of the same order of magnitude than the viscothermal linear losses and modifie the functioning of the whole instrument. For real-time synthesis purposes, a simplified algorithm is proposed and compared to the more accurate model.
Download A Stable Acoustic Impedance Model of the Clarinet using Digital Waveguides
Digital waveguide (DW) modeling techniques are typically associated with a traveling-wave decomposition of wave variables and a “reflection function” approach to simulating acoustic systems. As well, it is often assumed that inputs and outputs to/from these systems must be formulated in terms of traveling-wave variables. In this paper, we provide a tutorial review of DW modeling of acoustic structures to show that they can easily accommodate physical input and output variables. Under certain constraints, these formulations reduce to simple “Schroeder reverb-like” computational structures. We also present a stable single-reed filter model that allows an explicit solution at the reed / air column junction. A clarinet-like system is created by combining the reed filter with a DW impedance model of a cylindrical air column.
Download The Mellin Pizzicator
In this paper an application of the Mellin transform to the digital audio effects will be presented. Namely, low-pass and band-pass like filtering in the Mellin domain will be described and used for obtaining some kind of pizzicato effect on audio samples (musical instruments, but not only). The pluck and damp effects will be obtained using filtering in Mellin domain only. The algorithm used for implementing the Mellin (scale) transform has been presented in DAFx’04 .
Download Fractal Modulation Effects
Fractal modulation is obtained by forming a power weighted superposition of scaled and modulated versions of the signal. The resulting signal is self-similar with fractal characteristics. In this paper we explore fractal modulation as a powerful method to generate rich signals, useful both for the synthesis of complex sounds, like the sounds from natural events or ecological sounds, or as control functions of audio effects. The wavelet transform can be used as an efficient tool in order to generate a subset of fractal modulated signals that are power homogeneous. Any signal used as a seed for fractal modulation is transformed into a multiscale sound by means of a tree-structured multirate filter bank. Moreover, by superimposing a structured modulation scheme one can generate pseudo-periodic sounds whose partials have fractal behavior.
Download An Interdisciplinary Approach to Audio Effect Classification
The aim of this paper is to propose an interdisciplinary classification of digital audio effects to facilitate communication and collaborations between DSP programmers, sound engineers, composers, performers and musicologists. After reviewing classifications reflecting technological, technical and perceptual points of view, we introduce a transverse classification to link disciplinespecific classifications into a single network containing various layers of descriptors, ranging from low-level features to high-level features. Simple tools using the interdisciplinary classification are introduced to facilitate the navigation between effects, underlying techniques, perceptual attributes and semantic descriptors. Finally, concluding remarks on implications for teaching purposes and for the development of audio effects user interfaces based on perceptual features rather than technical parameters are presented.