Download Real-Time Bayesian GSM Buzz Removal In this paper we propose an iterative audio restoration algorithm based on an autoregressive (AR) model with modeling of the noise pulse template to detect and restore Cell-phone electromagnetic interference (EMI) patterns known as “GSM buzz”. The algorithm is purely software based and does not require the aid of any hardware providing side information. The only assumption is that individual pulses are similar to scaled versions of the known template. With this assumption, the algorithm can fully detect and restore noisy interference signals in real time with almost no audible artifacts and improve the signal to noise ratio by as much as 50dB.
Download Single-Note Ornamentation Transcription for the Irish Tin Whistle Based on Onset Detection Ornamentation plays a very important role in Irish Traditional music, giving more expression to the music by altering or embellishing small pieces of a melody. Single-note ornamentation, such as cuts and strikes, are the most common type in Irish Traditional music and are played by articulating the note pitch during the onset stage. A technique for transcribing single note ornamentation for the tin whistle based on onset detection is presented. This method focuses on the characteristics of the tin whistle within Irish traditional music, customising a time-frequency based representation for detecting the instant when new notes played using single-note ornamentation start and release.
Download A reverberator based on absorbent all-pass filters Artificial reverberator topologies making use of all-pass filters in a feedback loop are popular, but have lacked accurate control of decay time and energy level. This paper reviews a general theory of artificial reverberators based on Unitary-Feedback Delay Networks (UFDN), which allow accurate control of the decay time at multiple frequencies in such topologies. We describe the design of an efficient reverberator making use of chains of elementary filters, called “absorbent all-pass filters”, in a feedback loop. We show how, in this particular topology, the late reverberant energy level can be controlled independently of the other control parameters. This reverberator uses the I3DL2 control parameters, which have been designed as a standard interface for controlling reverberators in interactive 3D audio.
Download Smoothing of the Control Signal without Clipped Output in Digital Peak Limiters This paper studies the reduction of nonlinearity of digital peak limiters used for maximizing signal levels. The goal is to control the time-varying gain smoothly enough to avoid frequency artifacts in the output signal. Smoother gain control is traditionally obtained by lowpass Þltering the gain or the signal envelope. However, simple Þltering causes overshoots and leads to either clipped output or non-maximal signal levels, depending on the gain applied to the limiter output. In order to obtain smooth gain control without clipping, this paper proposes an envelope detection method based on order-statistics Þltering.
Download A real-time audio rendering system for the Internet (iARS), embedded in an electronic music library (IAEM) The internet Audio Rendering System (iARS) is an Internet browser extension extending the browser’s capabilities with real-time signal processing. The proposed system allows to receive audio streams from the Internet and apply various audio algorithms with no additional computational power needed from the server. iARS is part of the Internet Archive of Electronic Music (IAEM) project which is also presented in this paper.The IAEM is intended to be a platform to access an extensive and distributed archive of electronic music. It combines collaborative tools, real time signal processing on the client side and the content of the archive to a powerful teaching, research and publishing tool.
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 Modulation and demodulation of steerable ultrasound beams for audio transmission and rendering Nonlinear effects in ultrasound propagation can be used for generating highly directive audible sound. In order to do so, we can modulate the amplitude of the audio signal and send it to an ultrasound transducer. When played back at a sufficiently high sound pressure level, due to a nonlinear behavior of the medium, the ultrasonic signal gets self-demodulated. The resulting signal has two important characteristics: that of becoming audible; and that of having the same directivity properties of the ultrasonic carrier frequency. In this paper we describe the theoretical advantages of singlesideband (SSB) modulation versus a standard amplitude modulation (AM) scheme for the above-described application. We describe our near-field soundfield measuring experiments, and propose steering solutions for the array using two different types of transducers, piezoelectric or electrostatic, and the proper supporting hardware.
Download Measuring Sensory Consonance by Auditory Modeling A current model of pitch perception is based on cochlear filtering followed by a periodicity detection. Such a computational model is implemented and then extended to characterise the sensory consonance of pitch intervals. A simple scalar measure of sensory consonance is developed, and to evaluate this perceptually related feature extraction the consonance is computed for musical intervals. The relation of consonance and dissonance to the psychoacoustic notions of roughness and critical bandwidth is discussed.
Download Interpolation of long gaps in audio signals using the warped Burg's method This paper addresses the reconstruction of missing samples in audio signals via model-based interpolation schemes. We demonstrate through examples that employing a frequency-warped version of Burg’s method is advantageous for interpolation of long duration signal gaps. Our experiments show that using frequencywarping to focus modeling on low frequencies allows reducing the order of the autoregressive models without degrading the quality of the reconstructed signal. Thus a better balance between qualitative performance and computational complexity can be achieved.