References of "Embrechts, Jean-Jacques"
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See detailA Diffraction Model for Acoustical Ray-Tracing Based on the Energy Flow Lines Concept
Billon, Alexis; Embrechts, Jean-Jacques ULg

in Acta Acustica United with Acustica (2013), 99

Geometrical acoustics models are currently the most popular prediction tools in room-acoustics due to their low computing load. However, they seldom take into account the diffraction occurring at free ... [more ▼]

Geometrical acoustics models are currently the most popular prediction tools in room-acoustics due to their low computing load. However, they seldom take into account the diffraction occurring at free edges. Moreover, the existing diffraction models implemented in geometrical acoustics algorithms are either limited to specularly reflected paths or either present excessive computation load. Recently, a diffraction model based on an approximation of the far-field direction of the Poynting’s vector around half-planes has been introduced for computing the scattering due to faceted dielectric objects. In this article, this model is developed to handle obliquely incident waves and is implemented within an acoustic ray-tracing software using the analogy between the Poynting’s and the acoustic intensity vectors. The proposed model can handle both diffuse and specular reflections and sets no limit in terms of reflection or diffraction order. The first results obtained by ray-tracing agree well with the uniform theory of diffraction and the boundary elements method for single and double diffraction problems even if the interference effects are neglected and as long as the number of emitted rays is sufficient. Moreover, the additional computation load to handle diffraction is shown to be low compared to the one from a classical ray-tracing algorithm. [less ▲]

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See detailSound for 3D Cinema and the Sense of Presence
André, Cédric ULg; Embrechts, Jean-Jacques ULg; Verly, Jacques ULg et al

in Nees, Michael A.; Walker, Bruce N.; Freeman, Jason (Eds.) Proceedings of the 18th International Conference on Auditory Display (2012, June 18)

While 3D cinema is becoming more and more established, little effort has focused on the general problem of producing a 3D sound scene spatially coherent with the visual content of a stereoscopic-3D (s-3D ... [more ▼]

While 3D cinema is becoming more and more established, little effort has focused on the general problem of producing a 3D sound scene spatially coherent with the visual content of a stereoscopic-3D (s-3D) movie. As 3D cinema aims at providing the spectator with a strong im- pression of being part of the movie (sense of presence), the perceptual relevance of such spatial audiovisual coherence is of significant interest. Previous research has shown that the addition of stereoscopic informa- tion to a movie increases the sense of presence reported by the spectator. In this paper, a coherent spatial sound rendering is added to an s-3D movie and its impact on the reported sense of presence is investigated. A short clip of an existing movie is presented with three different sound- tracks. These soundtracks differ by their spatial rendering quality, from stereo (low spatial coherence) to Wave Field Synthesis (WFS, high spatial coherence). The original stereo version serves as a reference. Results show that the sound condition does not impact on the sense of presence of all participants. However, participants can be classified according to three different levels of presence sensitivity with the sound condition impacting only on the highest level (12 out of 33 participants). Within this group, the spatially coherent soundtrack provides a lower reported sense of presence than the other custom soundtrack. The analysis of the participants’ heart rate variability (HRV) shows that the frequency-domain parameters correlate to the reported presence scores. [less ▲]

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See detailNon-linear loudspeaker simulation. Guitar loudspeaker.
Schmitz, Thomas ULg; Embrechts, Jean-Jacques ULg

Conference (2012, June 06)

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See detailEvaluation of the acoustic comfort of air-treatment systems with a multi-task procedure
Minard, Antoine; Robin, Benjamin; Fournier, Francette et al

in E.A.A. (Ed.) Proceedings of the 2012 Euronoise Congress (2012, June)

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See detailNeural networks for musical chords recognition
Osmalsky, Julien ULg; Embrechts, Jean-Jacques ULg; Van Droogenbroeck, Marc ULg et al

in Journées d'informatique musicale (2012, May)

In this paper, we consider the challenging problem of music recognition and present an effective machine learning based method using a feed-forward neural network for chord recognition. The method uses ... [more ▼]

In this paper, we consider the challenging problem of music recognition and present an effective machine learning based method using a feed-forward neural network for chord recognition. The method uses the known feature vector for automatic chord recognition called the Pitch Class Profile (PCP). Although the PCP vector only provides attributes corresponding to 12 semi-tone values, we show that it is adequate for chord recognition. Part of our work also relates to the design of a database of chords. Our database is primarily designed for chords typical of Western Europe music. In particular, we have built a large dataset filled with recorded guitar chords under different acquisition conditions (instruments, microphones, etc), but also with samples obtained with other instruments. Our experiments establish a twofold result: (1) the PCP is well suited for describing chords in a machine learning context, and (2) the algorithm is also capable to recognize chords played with other instruments, even unknown from the training phase. [less ▲]

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See detailTimbre description of the sound of air-treatment systems for predicting acoustic confort
Minard, Antoine; Billon, Alexis ULg; Goujard, B. et al

Poster (2012, April)

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See detailDiscrimination thresholds of the reverberation in large volumes by naïve listeners
Billon, Alexis ULg; Embrechts, Jean-Jacques ULg

in Proceedings of the Acoustics 2012 Nantes conference (2012, April)

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See detailRay-tracing modelling of the diffraction by half-planes and slits based on the energy flow lines concept
Billon, Alexis ULg; Embrechts, Jean-Jacques ULg

in Proceedings of the Acoustics 2012 Nantes conference (2012, April)

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See detailLes haut-parleurs électrodynamiques
Embrechts, Jean-Jacques ULg

Learning material (2012)

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See detailSearching for a theoretical relation between reverberation and the scattering coefficients of surface in a room
Embrechts, Jean-Jacques ULg

in Proceedings of the Acoustics 2012 Nantes conference (2012, April)

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See detailAURALIAS: an audio-immersive system for auralizing room acoustics projects
Embrechts, Jean-Jacques ULg

Conference (2011, December)

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See detailMicrophone arrays fundamentals
Embrechts, Jean-Jacques ULg

Conference (2011, November 23)

Microphone arrays are essentially directional sensors. They are therefore mainly used for locating, identifying, isolating, measuring and recording individual sound sources. The main principles governing ... [more ▼]

Microphone arrays are essentially directional sensors. They are therefore mainly used for locating, identifying, isolating, measuring and recording individual sound sources. The main principles governing the directivity of microphone arrays are reviewed: phase differences between signals create constructive and destructive interferences, depending on the direction of the sound source. Moreover, signal processing is applied to provide “beamforming”, i.e. beam shaping and steering. Contrary to continuous antenna, discrete arrays can create aliasing, which can result in false detections of sound sources. The delay-and-sum and filter-and-sum beamformers are described. Finally, as simple beamformers are often frequency dependent, some solutions to obtain constant (broad-band) directivity are presented. [less ▲]

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See detailObject-Based Sound Re-Mix for Spatially Coherent Audio Rendering of an Existing Stereoscopic-3D Animation Movie
Evrard, Marc ULg; André, Cédric ULg; Verly, Jacques ULg et al

Conference (2011, October 20)

While 3D cinema is becoming more established, little effort has focused on the general problem of producing a 3D sound scene spatially coherent with the visual content of a stereoscopic-3D (s-3D) movie ... [more ▼]

While 3D cinema is becoming more established, little effort has focused on the general problem of producing a 3D sound scene spatially coherent with the visual content of a stereoscopic-3D (s-3D) movie. The perceptual relevance of such spatial audiovisual coherence is of significant interest. In order to carry out such experiments, it is necessary to have an appropriate s-3D movie and its corresponding 3D audio track. This paper presents the procedure followed to obtain this joint 3D video and audio content from an existing animated s-3D film, problems encountered, and some of the solutions employed. [less ▲]

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See detailNumerical evidence of mixing in rooms using the free path temporal distribution
Billon, Alexis ULg; Embrechts, Jean-Jacques ULg

in Journal of the Acoustical Society of America (2011), 130(3), 13811389

The ergodic propriety of a room has strong effects on its reverberation. If the room is ergodic, the reverberation can be broken up in two steps: a deterministic process followed by a stochastic one. The ... [more ▼]

The ergodic propriety of a room has strong effects on its reverberation. If the room is ergodic, the reverberation can be broken up in two steps: a deterministic process followed by a stochastic one. The late reverberation can be then modeled by a reverberation algorithm instead of more computationally consuming methods. In this study, the free path temporal distribution obtained by ray-tracing is used as an indicator of the room’s mixing: the energetic average of the path lengths is computed at each time step. Ergodic rooms are thus characterized by rapidly convergent distributions. The free path value becomes independent of time. On the other hand, path selection mechanism and orbits are observed in non-ergodic rooms. The transition time from the deterministic process to the stochastic one is also studied through the evaluation of the room’s time constant. It is shown that its value depends only on the mean free path and the boundaries scattering value. An empirical expression is obtained which agrees well with simulations carried out in a concert hall. This transition time from a deterministic model to a stochastic one can be used to speed up the acoustical predictions and auralizations in ergodic rooms. [less ▲]

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See detailAcoustic comfort of air-treatment systems: influence of factors related to room acoustics
Minard, Antoine; Goujard, Bertrand; Sakout, Anas et al

Conference (2011, June 30)

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See detailRay-tracing modelling of the diffraction by half-planes based on the energy flow lines concept
Billon, Alexis ULg; Embrechts, Jean-Jacques ULg

in Proceedings of the Forum Acusticum 2011 Congress (2011, June 28)

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See detail3D Audio Acquisition and Reproduction Systems
Evrard, Marc ULg; André, Cédric ULg; Embrechts, Jean-Jacques ULg et al

Scientific conference (2011, February 23)

This presentation introduces two different research projects dealing with 3D audio for 3D-stereoscopic movies. The first project “3D audio acquisition for real time applications” studies the best method ... [more ▼]

This presentation introduces two different research projects dealing with 3D audio for 3D-stereoscopic movies. The first project “3D audio acquisition for real time applications” studies the best method for acquiring a full 3D audio soundscape on location and for processing it in real-time for further reproduction. The second project “Adding 3D sound to 3D cinema” is aimed towards the study of reproducing a 3D soundscape consistent with the visual content of a 3D-stereoscopic movie. These projects are linked together since they present both ends of the 3D audio chain. They are conducted as part of the “MEDIATIC – 3D MEDIA” project, which concerns the production, the processing, and the exploitation of rich audiovisual content, with a specific focus on 3D video imagery. [less ▲]

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See detailTheoretical Determination of the Random-Incidence Scattering Coefficients of Infinite Rigid Surfaces with a Periodic Rectangular Roughness Profile
Embrechts, Jean-Jacques ULg; Billon, Alexis ULg

in Acta Acustica United with Acustica (2011), 97

An exact solution is developed for the sound field reflected by an infinite rigid rough surface with a periodic rectangular profile. The random-incidence scattering coefficient of this surface is derived ... [more ▼]

An exact solution is developed for the sound field reflected by an infinite rigid rough surface with a periodic rectangular profile. The random-incidence scattering coefficient of this surface is derived from the numerical calculation of this solution for several directions of the incident plane wave. Scattering coefficients’ values are given in this paper for a great number of configurations by varying the geometrical parameters of the periodic profile, leading to a very detailed description of the scattering properties of this kind of profile. In particular, it is shown that, when the ratio H/L of the depth to the spatial period of the profile is small, the key parameter is H/, the ratio of the depth of the profile to the wavelength. The random-incidence scattering coefficient tends to increase with this ratio, as long as H/ is less than 0.3. This evolution is similar to gaussian and sine-shaped profiles analysed in previous studies. For H/ >0.3, the coefficient’s value oscillates while converging to an asymptotic value which depends on the width of the wells. Resonance effects have also been highlighted for periodic rectangular profiles, in particular by comparing the computed scattering coefficients with the few measured values published in the scientific literature. The scattering coefficients’ values published in this paper can be introduced in room acoustics’ models to characterize periodic rectangular surfaces, provided that their dimensions are much greater than the wavelength. Additional measurements and BEM computations are required to deeply analyse the influence of the finite size and the acoustical absorption of real surfaces having this profile. [less ▲]

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See detailResearch activities in 3D sound and Auralization (in Intelsig)
Embrechts, Jean-Jacques ULg

Poster (2010, December)

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