Download Digital Filtering for Musicians The CD-ROM Digital Filtering for Musicians was made to build a bridge between two very diverse, yet interrelated topics; digital audio techniques and music, with the main focus on one of the central techniques: filtering. To make optimal use of digital filtering in a musical context requires insight in mathematics and computational theory as well as music. By presenting these three fields side-by-side on an interactive basis, readers can familiarize themselves with the relevant topics and their relations, without being overwhelmed by the complexity of the subject.
Download Software modules for HRTF based dynamic spatialisation This paper describes the object oriented design and development of software modules intended to enhance multimedia presentations with sound sources spatialisation, and environmental effects (reverberation), allowing dynamic reconfiguration of the input sound parameters. Implementations have been carried out on a PC platform, on top of the Win32 API. The resulting modules (in fact C++ classes) have later been integrated into a working application for demonstration purposes.
Download AudioBIFS: The MPEG-4 Standard for Effects Processing We present a tutorial overview of the AudioBIFS system, part of the Binary Format for Scene Description in the MPEG-4 International Standard. AudioBIFS allows the flexible construction of sound scenes using streaming audio, interactive presentation, 3-D spatialization and environmental auralization, and dynamic download of custom signal-processing routines. MPEG-4 sound scenes are based on a model that is a superset of the model in VRML 2.0, and a comparison between the two models is presented. We discuss the use of SAOL, the MPEG-4 Structured Audio Orchestra Language, for writing downloadable effects. The current status of the standard is described.
Download Vibrato extraction and parameterization in the Spectral Modeling Synthesis framework Periodic or quasi-periodic low-frequency components (i.e. vibrato and tremolo) are present in steadystate portions of sustained instrumental sounds. If we are interested both in studying its expressive meaning, or in building a hierarchical multi-level representation of sound in order to manipulate it and transform it with musical purposes those components should be isolated and separated from the amplitude and frequency envelopes. Within the SMS analysis framework it is now feasible to extract high level time-evolving attributes starting from basic analysis data. In the case of frequency envelopes we can apply STFTs to them, then check if there is a prominent peak in the vibrato/tremolo range and, if it is true, we can smooth it away in the frequency domain; finally, we can apply an IFFT to each frame in order to re-construct an envelope that has been cleaned of those quasi-periodic low-frequency components. Two important problems nevertheless have to be tackled, and ways of overcoming them will be discussed in this paper: first, the periodicity of vibrato and tremolo, that is quite exact only when the performers are professional musicians; second: the interactions between formants and fundamental frequency trajectories, that blur the real tremolo component and difficult its analysis.
Download Morph: Timbre Hybridization Tools Based on Frequency Domain Processing This paper presents a hybridization method using Morph, a sound timbre hybridization and modeling software running on the Windows 95 platform. Elaboration occurs in Fourier space and is based on analysis/re-synthesis operations through FFT and FFT-1. The hybridization method works through the segmentation of two starting spectra in zones centered on the energy peaks. Each identified spectral zone, is numbered in increasing order so that a matching can be established between pairs of zones with the same value during re-synthesis. A full description of the Morph elaboration performance includes cross-synthesis, timbre hybridization, harmonic/inharmonic component separation and filtering. An initial catalogue of hybrid sounds has been compiled using this system, in order to tackle hybridization problems in an organic and systematic manner. The criteria used for the drafting and organization of the catalogue are discussed in the latter part of this paper.
Download Extracting More Detail from the Spectrum with Phase Distortion Analysis In the sinusoidal analysis of sound, using the Short Time Fourier Transform (STFT), there is the assumption that the signal is locally stationary within each FFT frame. If, as in practice, this assumption is violated, the spectrum becomes distorted. Phase Distortion Analysis (PDA) was introduced in 1995 [1] to enhance the analysis of degraded peaks, by using the distortion itself as a source of information about the signal nonstationarity. It was shown that the first order frequency and amplitude modulation could be measured from the degree of phase shift close to the maximum of the mainlobe peak. This paper presents advances with the PDA technique, in particular a neural network implementation that makes estimation robust to noise. The capability to analyse nonstationarities relaxes the restraint on keeping the FFT analysis window short and therefore effectively improves time-frequency resolution. This, in turn, promises greater analysis-synthesis quality through improved identification and tracking of partials during the analysis phase.
Download SMSPerformer: A real-time synthesis interface for SMS SmsPerformer is a graphical interface for the real-time SMS synthesis engine. The application works from analyzed sounds and it has been designed to be used both as a composition and a performance tool. The program includes programmable time-varying transformations, MIDI control for the synthesis parameters, and performance loading and saving options.
Download A Real-Time DSP-based Reverberation System with Computer This paper describes a highly versatile, low-cost reverberation system comprising two main elements: a computer for building and editing the desired reverberation effect impulse response, and a commercial DSP-based board, to run the algorithm in real-time, allowing the evaluation of the results. The main parameters of the reverberation algorithm can be modified by means of a dedicated graphic interface in the host computer.
Download Software Toolbox for Multichannel Sound Reproduction This paper describes a versatile software toolbox, which has been developed for researching, teaching and developing in the field of multichannel sound signal processing. The software system runs on a PC and consists on 5 modules covering the main stages and aspects of multichannel sound reproduction using loudspeakers. A number of new and efficient algorithms have been specially implemented for this software.
Download Using Ideas from Natural Selection to Evolve Synthesized Sounds This paper describes a system for the automatic creation of digital synthesizer circuits that can generate sounds similar to a sampled (target) sound. The circuits will consist of very basic signal functions and generators that are arbitrarily interconnected. The system uses a “genetic algorithm” (GA) to evolve successively better circuits. First it creates populations of such synthesizers, generates the output and a fitness value of each individual circuit. The ones that are best at imitating the target sound will be kept. They are used for “breeding” to form a new generation where, hopefully, at least some individuals perform better than their parents did. The end result will be a circuit that can create a sound that resembles the target sample. Because it’s a synthesizer we can manipulate the different parameters when generating the sound. We can also get a very compact representation of the sound that can be useful when distributing music over a limited bandwidth communications channel (e.g. Internet). As we shall see, it also gives the user a very powerful tool for creating totally new sounds.