Download Examples of the musical use of digital audio effects This tutorial gives examples of the musical use of digital audio effects, drawn mostly from my computer music pieces Sud and Invisible. Rather than on the technical implementation, the emphasis will be placed upon the musical purpose of the effects, called for in order to simulate large spaces and illusory source movements; to create transposed echoes or choruses; to stretch words and sentences in time; to imprint selected pitches or harmonies onto sounds of natural origin.
Download Fractionally-addressed Delay Lines While traditional implementations of digital delay lines are based on a circular buffer accessed by two pointers, we propose an implementation where a single fractional pointer is used both for reading and writing operations. On modern general-purpose architectures, the proposed method is nearly as efficient as the popular interpolated circular buffer, but it offers better performance in terms of frequency-dependent attenuation and response to delay-length modulations.
Download Design and implementation of a 3-D sound system based on the HRTF Virtual Reality is one of the hottest buzzwords today in electronics industry. Until recently, the focus of these efforts was in providing stereoscopic three-dimensional graphics to stimulate our sense of vision. However, to create believable worlds, visual cues are not sufficient, the field of auralization, -three dimensional sound- is necessary. There are a number of motivations for developing auralization systems in addition to the advent of virtual reality. The three dimensional processing adds an auxiliary creative element to be manipulated by the commercial musician or record producer, providing a new realm of entertainment to explore. In this paper, a tridimensional sound system for performing static sound source placement with headphone playback using the filtering by HRTF is developed.
Download Sonic Screwdrivers: Sound as a Sculptural Process This paper discusses a Fine Art approach to the processes of digital audio. The author puts forward some ideas for a re-defining of digital audio software to embrace a wider audience and to promote the manipulation of sound as a sculptural process removed from, yet still related to, the assumed musical tradition. The authors artworks are introduced, and the impact of current research upon these artworks and upon the authors teaching are discussed.
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 Sound Transformations Based on the SMS High Level Attributes The basic Spectral Modeling Synthesis (SMS) technique models sounds as the sum of sinusoids plus a residual. Though this analysis/synthesis system has proved to be successful in transforming sounds, more powerful and intuitive musical transformations can be achieved by moving into the SMS high-level attribute plane. In this paper we describe how to extract high level sound attributes from the basic representation, modify them, and add them back before the synthesis stage. In this process new problems come up for which we propose some initial solutions.
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 Time Scale Modification Using a Sines+Transients+Noise Signal Model We propose a method for the time scaling of digitally sampled audio signals using a three part signal model consisting of sines+transients+noise. The three part model provides an accurate and flexible parametric representation for a wide range of audio signals. Because the proposed time scaling method manipulates each of the model components separately, the method allows modified tonal components of the signal to preserve pitch, transient components of the signal to preserve edges and noise-like components of the signal to remain noisy. The method therefore provides robust and natural sounding time scale modifications for a large variety of signals.
Download A Hilbert-Transformer Frequency Shifter for Audio In contrast to conventional pitch-shifting effects which attempt to maintain harmonic relationships in the signal, a frequency shifter translates all the component frequencies of the input signal by an equal amount, disrupting the harmonic relationships and radically altering the sonic qualities of the signal. Ring modulation is a generalization of double-sideband suppressed-carrier modulation, and the frequency shifter is equivalent to a single-sideband modulator. Applications of the frequency shifter include the creation of bizarre distortions, phaser, and rotating speaker effects. An implementation is presented that is suitable for fixed-point digital hardware.