Download Application of Raster Scanning Method to Image Sonification, Sound Visualization, Sound Analysis and Synthesis Raster scanning is a technique for generating or recording a video image by means of a line-by-line sweep, tantamount to a data mapping scheme between one and two dimensional spaces. While this geometric structure has been widely used on many data transmission and storage systems as well as most video displaying and capturing devices, its application to audio related research or art is rare. In this paper, a data mapping mechanism of raster scanning is proposed as a framework for both image sonification and sound visualization. This mechanism is simple, and produces compelling results when used for sonifying image texture and visualizing sound timbre. In addition to its potential as a cross modal representation, its complementary and analogous property can be applied sequentially to create a chain of sonifications and visualizations using digital filters, thus suggesting a useful creative method of audio processing. Special attention is paid to the rastrogram - raster visualization of sound - as an intuitive visual interface to audio data. In addition to being an efficient means of sound representation that provides meaningful display of significant auditory features, the rastrogram is applied to the area of sound analysis by visualizing characteristics of loop filters used for a Karplus-Strong model. A new sound synthesis method based on texture analysis/synthesis of the rastrogram is also suggested.
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 Parameterized Morphing as a Mapping Technique for Sound Synthesis We present a novel mapping technique for sound synthesis. The technique extends the familiar concept of morphing to the domain of synthesis parameters. A morph between defined points in the parameter space representing desirable sounds is itself parameterized with high-level controls. The choice of end points of the morph and the extent of the morph are used as input handles to map arbitrary control signals to the synthesis parameters. Additional off-line methods control the interpolation functions and selection of parameter points. We discuss a tool to allow creation, manipulation and usage of such mappings.
Download Variable Pre-Emphasis LPC for Modeling Vocal Effort in the Singing Voice In speech and singing, the spectral envelope of the glottal source varies according to different voice qualities such as vocal effort, lax voice, and breathy voice. In contrast, linear prediction coding (LPC) models the glottal source in a way that is not flexible. The spectral envelope of the source estimated by LPC is fixed and determined by the pre-emphasis filter. In standard LPC, the formant filter captures variation in the spectral envelope that should be associated with the source. This paper presents variable preemphasis LPC (VPLPC) as a technique to allow the estimated source to vary. This results in formant filters that remain more consistent across variations in vocal effort and breathiness. VPLPC also provides a way to change the envelope of the estimated source, thereby changing the perception of vocal effort. The VPLPC algorithm is used to manipulate some voice excerpts with promising but mixed results. Possible improvements are suggested.
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 Detection of Room Reflections from a Binaural Room Impulse Response A novel analysis method for binaural room impulse responses (BRIRs) is presented. It is based on the analysis of ear canal signals with continuous wavelet transform (CWT). Then, the crosswavelet transform (XWT) is used for detection of the direct sound and individual reflections from a BRIR. The new method seems to time-localize the reflections quite accurately. In addition, the proposed analysis method enables detailed study of the frequency content of the early reflections. The algorithm is tested with both measured and modeled impulse responses. A comparison with an FFT-based cross-spectrogram is made. The results show that XWT has potential in audio signal analysis.
Download Using Visual Textures for Sonic Textures Production and Control This work takes place in the framework of a global research on the synthesis of sonic textures and its control through a gesturebased interaction in a musical practice. In this paper we present different strategies to link visual and sonic textures using similar synthesis processes; theoretical considerations underlying to this problematic are firstly exposed and several personal realizations, illustrating different approaches to design a gesturally controlled audio-visual system, are then described.
Download Parametric Coding of Stereo Audio Based on Principal Component Analysis Low bit rate parametric coding of multichannel audio is mainly based on Binaural Cue Coding (BCC). Another multichannel audio processing method called upmix can also be used to deliver multichannel audio, typically 5.1 signals, at low data rates. More precisely, we focus on existing upmix method based on Principal Component Analysis (PCA). This PCA-based upmix method aims at blindly create a realistic multichannel output signal while BCC scheme aims at perceptually restitute the original multichannel audio signal. PCA-based upmix method and BCC scheme both use spatial parameters extracted from stereo channels to generate auditory events with correct spatial attributes i.e. sound sources positions and spatial impression. In this paper, we expose a multichannel audio model based on PCA which allows a parametric representation of multichannel audio. Considering stereo audio, signals resulting from PCA can be represented as a principal component, corresponding to directional sources, and one remaining signal, corresponding to ambience signals, which are both related to original input with PCA transformation parameters. We apply the analysis results to propose a new parametric coding method of stereo audio based on subband PCA processing. The quantization of spatial and energetic parameters is presented and then associated with a state-of-the-art monophonic coder in order to derive subjective listening test results.