Download Blind Source Separation Using Repetitive Structure Blind source separation algorithms typically involve decorrelating time-aligned mixture signals. The usual assumption is that all sources are active at all times. However, if this is not the case, we show that the unique pattern of source activity/inactivity helps separation. Music is the most obvious example of sources exhibiting repetitive structure because it is carefully constructed. We present a novel source separation algorithm based on spatial time-time distributions that capture the repetitive structure in audio. Our method outperforms time-frequency source separation when source spectra are highly overlapping.
Download Intermodulation Effects Analysis using Complex Bandpass Filterbanks The objective of this paper is to show the ability of complex bandpass filterbanks to extract the intermodulation information that appears when two audio signals interact inside the same analysis band. To perform the analysis a sinusoidal model of the signals has been assumed. Three kinds of signals have been analyzed: a sum of two cosines, a sum of two linear chirps and a sum of two exponential chirps. The complex bandpass filtering of the signals is carried out using a new algorithm based on the Complex Continuous Wavelet Transform. The developed algorithm has been validated comparing the practical results with the theoretical instantaneous amplitude and instantaneous phase of the obtained model of the signals. With the appropriate width, the complex bandpass filters show the same behaviour as our perceptual ability to discriminate interacting tones when they fall inside a critical band of the human ear.
Download Enhanced digital models for analog modulation effects This paper presents digital models for analog phaser and flanger / chorus effects. The structure of analog phasers is reviewed. The operation of two phaser implementations is analyzed and nonlinear digital models are presented for them. The models are based on cascades of one-pole filters with embedded nonlinearities and are suitable for real-time implementation. Modifications to standard digital flanger / chorus effect are also presented. A method to warp the delay time to more closely resemble the behavior of bucket brigade delays is presented. Also a simple model for companders used in such analog effect units is presented.
Download j-DAFx - Digital Audio Effects in Java This paper describes an attempt to provide an online learning platform for digital audio effects. After a comprehensive study of different technologies presenting multimedia content dynamically reacting to user input, we decided to use Java Applets. Further investigations regard the implementation issues - especially the processing and visualization of audio data - and present a general framework used in our department. Recent and future digital effects implemented in this framework can be found on our web site.
Download A library for realtime 3D binaural sound reproduction in pure data(PD) This paper presents a library for programming 3D binaural sound reproduction systems using Pure Data (pd), an open source computer music programming language. The theory that forms the basis of the proposed library is an improved virtual Ambisonics approach. Using this approach provides computationally efficient implementation of multiple moving sound sources, room simulation, head tracking and time varying listener positions in virtual space. Furthermore, simple GUI objects for controlling parameters are implemented to provide easy to use environment.
Download Everyday sounds with the digital Intonarumori A digital simulation of the Intonarumori, musical instruments invented by the Italian Futurist composer and painter Luigi Russolo is proposed. By building physical models of different members of the Intonarumori family, a preservation of an important contribution to the musical heritage of the beginning of the 20th century is achieved.
Download Sound quality of an Augmented Reality Audio headset In augmented reality audio applications the user is exposed to a pseudo-acoustic reproduction of the real acoustic environment. This means that the surrounding sounds are heard through a specific augmented reality audio (ARA) headset [1]. Ideally the pseudoacoustic environment should be an exact copy of the real acoustic environment. The acceptability and usefulness of such a headset depends strongly on the overall sound quality of the headset. Especially if the headset is to be worn for longer periods of time in everyday life situations, the sound quality of the system must be sufficient. In this paper an introduction to the aspects affecting the sound quality of an ARA-headset is addressed. In addition, results of a listening test for the overall sound quality of a well equalized headset are presented.
Download Fast implementation for non-linear time-scaling of stereo signals In this paper we present an improved implementation of Duxbury’s adaptive phase-vocoder approach for audio time-stretching using non-linear time-scaling and temporal masked phase locking at transients [1]. We show that the previous algorithm has some limitations, notably its slow implementation and its incapacity to deal with stereo signals. We propose solutions to this problems including: an improved transient detection, a much faster implementation using the IFFT for re-synthesis and a method for stretching stereo signals without artifacts. Finally, we provide some graphical results and quantitative measures to illustrate our improvements.
Download Morphing techniques for enhanced scat singing In jazz, scat singing is a phonetic improvisation that imitates instrumental sounds. In this paper, we propose a system that aims to transform singing voice into real instrument sounds, extending the possibilities for scat singers. Analysis algorithms in the spectral domain extract voice parameters, which drive the resulting instrument sound. A small database contains real instrument samples that have been spectrally analyzed offline. Two different prototypes are introduced, producing sounds of a trumpet and a bass guitar respectively.