Temporal distribution of information for human consonant recognition in VCV utterances

The temporal distribution of perceptually relevant information for consonant recognition in British English VCVs is investigated. The information distribution in the vicinity of consonantal closure and release was measured by presenting initial and final portions, respectively, of naturally produced VCV utterances to listeners for categorization. A multidimensional scaling analysis of the results provided highly interpretable, four-dimensional geometrical representations of the confusion patterns in the categorization data. In addition, transmitted information as a function of truncation point was calculated for the features manner place and voicing. The effects of speaker, vowel context, stress, and distinctive feature on the resulting information distributions were tested statistically. It was found that, although all factors are significant, the location and spread of the distributions depends principally on the distinctive feature, i.e., the temporal distribution of perceptually relevant information is very different for the features manner, place, and voicing

L'apport des informations visuelles des gestes oro-faciaux dans le traitement phonologique des phonèmes natifs et non-natifs : approches comportementale, neurophysiologique

During audiovisual speech perception, like in face-to-face conversations, we can takeadvantage of the visual information conveyed by the speaker's oro-facial gestures. Thisenhances the intelligibility of the utterance. The aim of this work was to determine whetherthis “audiovisual benefit” can improve the identification of phonemes that do not exist in ourmother tongue. Our results revealed that the visual information contributes to overcome thephonological deafness phenomenon we experience in an audio only situation (Study 1). AnERP study indicates that this benefit could be due to the modulation of early processing in theprimary auditory cortex (Study 2). The audiovisual presentation of non native phonemesgenerates a P50 that is not observed for native phonemes. The linguistic background affectsthe way we use visual information. Early bilinguals take less advantage of the visual cuesduring the processing of unfamiliar phonemes (Study 3). We examined the identificationprocesses of native plosive consonants with a gating paradigm to evaluate the differentialcontribution of auditory and visual cues across time (Study 4). We observed that theaudiovisual benefit is not systematic. Phoneme predictability depends on the visual saliencyof the articulatory movements of the speaker.En situation de perception audiovisuelle de la parole, comme lors des conversations face-àface,nous pouvons tirer partie des informations visuelles fournies par les mouvements orofaciauxdu locuteur. Ceci améliore l’intelligibilité du discours. L'objectif de ce travail était dedéterminer si ce « bénéfice audiovisuel » permet de mieux identifier les phonèmes quin’existent pas dans notre langue. Nos résultats révèlent que l’utilisation de l’informationvisuelle permet de surmonter les difficultés posées par la surdité phonologique dont noussommes victimes lors d'une présentation auditive seule (Etude 1). Une étude EEG indique quel’apport des informations visuelles au processus d’identification de phonèmes non natifspourrait être dû à une modulation précoce des traitements effectués par le cortex auditifprimaire (Etude 2). En présentation audiovisuelle les phonèmes non natifs donnent lieu à uneP50, ce qui n’est pas observé pour les phonèmes natifs. Il semblerait également quel'expérience linguistique affecte l'utilisation des informations visuelles puisque des bilinguesprécoces semblent moins aptes à exploiter ces indices pour distinguer des phonèmes qui neleur sont pas familiers (Etude 3). Enfin, l’étude de l’identification de consonnes plosivesnatives avec une tâche de dévoilement progressif nous a permis d’évaluer la contributionconjointe et séparée des informations auditives et visuelles (Etude 4). Nous avons observé quel’apport de la modalité visuelle n’est pas systématique et que la prédictibilité de l’identité duphonème dépend de la saillance visuelle des mouvements articulatoires du locuteur

Effects of forensically-relevant facial concealment on acoustic and perceptual properties of consonants

This thesis offers a thorough investigation into the effects of forensically-relevant facial concealment on speech acoustics and perception. Specifically, it explores the extent to which selected acoustic-phonetic and auditory-perceptual properties of consonants are affected when the talker is wearing ‘facewear’ while speaking. In this context, the term ‘facewear’ refers to the various types of face-concealing garments and headgear that are worn by people in common daily communication situations; for work and leisure, or as an expression of religious, social and cultural affiliation (e.g. surgical masks, motorcycle helmets, ski and cycling masks, or full-face veils such as the niqāb). It also denotes the face or head coverings that are typically used as deliberate (visual) disguises during the commission of crimes and in situations of public disorder (e.g. balaclavas, hooded sweatshirts, or scarves). The present research centres on the question: does facewear influence the way that consonants are produced, transmitted, and perceived? To examine the effects of facewear on the acoustic speech signal, various intensity, spectral, and temporal properties of spoken English consonants were measured. It was found that facewear can considerably alter the acoustic-phonetic characteristics of consonants. This was likely to be the result of both deliberate and involuntary changes to the talker’s speech productions, and of sound energy absorption by the facewear material. The perceptual consequences of the acoustic modifications to speech were assessed by way of a consonant identification study and a talker discrimination study. The results of these studies showed that auditory-only and auditory-visual consonant intelligibility, as well as the discrimination of unfamiliar talkers, may be greatly compromised when the observer’s judgements are based on ‘facewear speech’. The findings reported in this thesis contribute to our understanding of how auditory and visual information interact during natural speech processing. Furthermore, the results have important practical implications for legal cases in which speech produced through facewear is of pivotal importance. Forensic speech scientists are therefore advised to take the possible effects of facewear on speech into account when interpreting the outcome of their acoustic and auditory analyses of evidential speech recordings, and when evaluating the reliability of earwitness testimony