1,721,045 research outputs found
Control of spatial impressions in virtual acoustic environments
No full textLes travaux présentés dans cette thèse participent à l'élaboration de nouveaux outils de conception d'un espace sonore pour la production de contenus immersifs. En particulier, ils visent à permettre le contrôle des impressions spatiales : la largeur apparente de source et l'enveloppement. Pour cela, plusieurs études ont été réalisées afin d'évaluer la perception de l'acoustique de salles selon une méthode de reproduction sonore communément employée dans ce contexte : un rendu binaural non-individualisé de scènes sonores encodées en ambisonique. Les contenus immersifs étant généralement composés d’un environnement visuel à 360° et d’une grande diversité de sources sonores, la première partie de cette thèse traite de l’influence de ces deux composantes sur la perception de l'acoustique d'une salle. La seconde partie aborde la paramétrisation de réponses impulsionnelles spatiales de salle (SRIRs) qui caractérisent le trajet acoustique entre la source sonore et l'auditeur. Nous avons cherché à optimiser les résolutions spatiales, fréquentielles et temporelles des SRIRs, permettant ainsi une réduction de la quantité de données et une meilleure appréhension du contrôle perceptif tout en conservant un rendu convenable de l'espace sonore. La dernière partie se concentre sur la modification de SRIRs pour le contrôle des impressions spatiales. Afin d'évaluer le contrôle de la largeur apparente de source, plusieurs transformations spatiales ont été appliquées aux signaux ambisoniques d'ordre 1 utilisés pour décrire les premières réflexions d'une SRIR. Une méthode de contrôle de la sensation d'enveloppement a été proposée en utilisant un réverbérateur artificiel qui permet la modification des amplitudes et pentes de décroissance de l'énergie sonore dans plusieurs bandes de fréquence et secteurs angulaires.The work presented in this thesis contributes to the development of new tools that facilitate the design of immersive sound spaces for the production of Virtual Reality contents.More specifically, we aimed to allow the control of spatial impressions : the apparent source width and the sensation of envelopment. To this end, several studies have been conducted to evaluate the perception of room acoustics using a non-individualized binaural rendering of ambisonic sound scenes, which is common in this context. Since immersive contents usually consist of a 360° visual environment and a wide variety of sound sources, the first part of this thesis focuses on the influence of these two components on the perception of room acoustics. The second part addresses the parameterization of Spatial Room ImpulseResponses (SRIRs), which are transfer functions that describe the acoustic path between the sound source and the listener.The spatial, temporal and frequency resolutions of SRIRs were studied to seek a possible reduction in the amount of data and thus a better apprehension of the perceptual control, while maintaining spatial and timbral fidelity. The last part focuses on the modification of SRIRs for the control of spatial impressions. In order to evaluate the control of the apparent source width, several spatial transformations were applied to the first-order ambisonic signals used to describe the early reflections of SRIRs. For the control of the sensation of envelopment, a method was proposed using an artificial reverberator that allows the modification of the sound energy amplitudes and decay slopes in several frequency bands and angular sectors
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Influence of the position of a sound source on loudness
No full textDans notre environnement quotidien, les sons nous parviennent depuis différentes distances et différentes directions. La sonie, qui désigne le niveau sonore perçu, dépend de la position relative (en distance et en direction) de la source sonore par rapport à l'auditeur. Cette thèse comporte deux parties distinctes s'intéressant à ces relations, l'une liant la sonie à l'azimut d'une source sonore et l'autre à la distance d'une source sonore frontale. La première partie étudie plus précisément les effets de sonie directionnelle liés aux différences interaurales de temps pour des sons basses fréquences. Ces différences, qui dépendent de l'azimut de la source et qui sont maximales lorsque la source se situe sur le côté de l'auditeur, provoquent une augmentation de sonie pour les sons basses fréquences. Cette augmentation de sonie est étudiée notamment en présence de bruit et en fonction de la validité écologique des conditions de présentation des sons. La seconde partie de cette thèse étudie deux types distincts de sonie (l'un correspondant au niveau sonore perçu « aux oreilles » et l'autre au niveau sonore perçu « à la source ») en fonction de la distance d’une source sonore en présence ou non d’indices visuels. Cette partie s'intéresse à des sons non-familiers (des bruits blancs) ainsi qu'à des sons familiers (des signaux de parole), ces derniers fournissant des informations aux auditeurs sur la puissance de leur source par le biais de leur timbre.In our daily environment, we perceive sounds coming from different distances and different directions. The loudness of these sounds depends on the relative position (in distance and direction) of their sources. This thesis is structured in two distinct parts studying these relations. One part focuses on links between loudness and sound source azimuth and the other on links between loudness and frontal sound source distance. The first part focuses more precisely on directionnal effects due to interaural time differences for lowfrequency sounds. These differences, which depend on the sound source azimuth and which are maximal when the source is located at the side of the listener, lead to an increase in loudness for low-frequency sounds.This loudness increase is studied when sounds are presented in noise and in presentation conditions with different ecological validity. The second part of this thesis focuses on two distinct kinds of loudness (one being the loudness « at the ears » and the other the loudness « at the source ») as a function of the distance of a sound source, with and without visual cues to the latter. This part studies unfamiliar (white noises) and familiar (speech) stimuli, the latters providing the listeners with information about their source power thanks to their timbre
Externalization in non-individualized binaural listening with head-tracking : objective and perceptive aspects
No full textLa restitution binaurale est une méthode de restitution du son au casque visant à simuler une écoute naturelle. Souvent, les sons restitués au casque semblent provenir de l’intérieur de la tête. Pour une restitution binaurale convaincante, les sons doivent paraître venir de l’extérieur (externalisés), comme dans la réalité. L’utilisation d’un système de suivi des mouvements de tête (head-tracking) peut permettre d’améliorer l’externalisation pendant et après les mouvements. Cette thèse examine l’effet de persistance de l’amélioration d’externalisation après des mouvements de tête. Une première étude a combiné une expérience comportementale et une expérience EEG pour identifier un corrélat neuronal de l’externalisation.Une méthode innovante, exploitant cet effet de persistance de l’externalisation, a été développée afin de comparer des stimuli "acoustiquement identiques", mais avec différents niveaux d’externalisation. Les résultats n’ont pas révélé de corrélat neuronal, mais ont soulevé plusieurs questions sur l’influence de la nature et de la durée des sources sonores sur l’effet de persistance de l’externalisation.Une deuxième étude, comportant trois expériences comportementales, a été menée afin d’aborder ces questions. Les résultats ont montré que l’amélioration d’externalisation après des mouvements de tête fonctionne pour différentes sources, mais diminue après une dizaine de secondes.Binaural reproduction is a method of sound playback through headphones aimed at simulating natural listening. Often, sounds played through headphones seem to originate from inside the head. For convincing binauralreproduction, sounds must appear to come from outside (externalized), as they do in reality.Using a head-tracking system can enhance externalization during and after headmovements. This thesis examines the persistence of the head movements after-effect on externalization. The first study combined a behavioral experiment and an EEG experiment to identify a neural correlate of externalization.An innovative method leveraging this after-effect was developed to compare "acoustically identical" stimuli with different levels of externalization. The results did not reveal a neural correlate but raised several questions about the influence of the nature and duration of sound sources on the head movements after-effect on externalization. A second study, involving three behavioral experiments, was conducted to address these questions. The results showed that the improvement in externalization after head movements works for various sound sources but decreases after about ten seconds
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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