Jean-Marc Jot

Real-time spatial processing of sounds for music, multimedia and interactive human-computer interfaces

Abstract. This paper gives an overview of the principles and methods for synthesizing complex 3D sound scenes by processing multiple individual source signals. Signal-processing techniques for directional sound encoding and rendering over loudspeakers or headphones are reviewed, as well as algorithms and interface models for synthesizing and dynamically controling room reverberation and distance effects. A real-time modular spatial-sound-processing software system, called Spat, is presented. It allows reproducing and controling the localization of sound sources in three dimensions and the reverberation of sounds in an existing or virtual space. A particular aim of the Spatialisateur project is to provide direct and computationally efficient control over perceptually relevant parameters describing the interaction of each sound source with the virtual space, irrespective of the chosen reproduction format over loudspeakers or headphones. The advantages of this approach are illustrated in practical contexts, including professional audio, computer music, multimodal immersive simulation systems, and architectural acoustics.

An analysis/synthesis approach to real-time artificial reverberation

A general approach is proposed to the problem of realizing a recursive digital display network capable of simulating in real time the perceptively relevant characteristics of the reverberation decay in a room. The analysis/synthesis method presented makes it possible to imitate the late reverberation of a given room by optimizing some of the reverberant filters parameters. The analysis phase is based on a time-frequency representation of the energy decay, computed from an impulse response measured in the room. The energy decay relief is proposed as a spectral development of the integrated energy decay curve introduced by Schroeder. Its three-dimensional representation allows perceptively relevant visual comparison of two room responses (measured or artificial) and accurate calculation of some widely used objective criteria of room acoustic quality.<<ETX>>

Analysis and synthesis of room reverberation in the time and frequency domains—Application to the restoration of room impulse responses corrupted by measurement noise.

This paper reviews a statistical time‐frequency model of the late diffuse reverberation in rooms. In this model, the later part of a room impulse response is described by a ‘‘time‐frequency envelope,’’ defined as the ensemble average of the time‐frequency energy distribution in the late decay. The time‐frequency envelope is independent of the source and receiver locations and is characterized by two functions of frequency: the reverberation time and a power spectral density called the ‘‘initial spectrum,’’ which corresponds to the product of the diffuse‐field transfer functions of the source and the receiver. An analysis method is described for deriving these parameters from a measured impulse response, yielding an accurate estimate of the reverberation time with arbitrary resolution in the frequency domain. The time‐frequency envelope defines a time‐dependent filter which transforms a sampled stationary Gaussian white noise into a synthetic model of the late reverberation decay. Substituting this synthet...

Validating a perceptual framework for dynamic auralization

The auralization of room impulse responses is generally realized by direct convolution with an anechoic signal. When using a simulated impulse response, the realism of the auralization relies mainly on the accuracy of the propagation model used to estimate time and spatial distributions of early reflections and of the reverberation process. An alternative approach, adopted at Ircam, uses a room effect synthesizer driven by acoustical indices, derived from the analysis of the response in order to describe the corresponding spatial, energetic, and statistical properties. Although the auralization performance then depends on the relevancy of these parameters, this latter solution offers the following advantages: (1) reduction of the computational cost; (2) manipulation of measured, estimated, and virtual configurations in a unified perceptual formalism; (3) adaptation to different reproduction format or setup, without recomputing the corresponding impulse responses. In order to validate the performance of th...