Voices are used as a vehicle for language, and variation in the acoustic properties of voices also contains information about the speaker. Listeners use measurable qualities, such as pitch and formant traits, as cues to a speaker’s physical stature and attractiveness. Emotional states and personality characteristics are also judged from vocal stimuli. The research contained in this thesis examines vocal masculinity, aesthetics and personality, with an emphasis on the perception of prosocial traits including trustworthiness and cooperativeness. I will also explore themes which are more cognitive in nature, testing aspects of vocal stimuli which may affect trait attribution, memory and the ascription of identity. Chapters 2 and 3 explore systematic differences across vocal utterances, both in types of utterance using different classes of stimuli and across the time course of perception of the auditory signal. These chapters examine variation in acoustic measurements in addition to variation in listener attributions of commonly-judged speaker traits. The most important result from this work was that evaluations of attractiveness made using spontaneous speech correlated with those made using scripted speech recordings, but did not correlate with those made of the same persons using vowel stimuli. This calls into question the use of sustained vowel sounds for the attainment of ratings of subjective characteristics. Vowel and single-word stimuli are also quite short – while I found that attributions of masculinity were reliable at very short exposure times, more subjective traits like attractiveness and trustworthiness require a longer exposure time to elicit reliable attributions. I conclude with recommending an exposure time of at least 5 seconds in duration for such traits to be reliably assessed. Chapter 4 examines what vocal traits affect perceptions of pro-social qualities using both natural and manipulated variation in voices. While feminine pitch traits (F0 and F0-SD) were linked to cooperativeness ratings, masculine formant traits (Df and Pf) were also associated with cooperativeness. The relative importance of these traits as social signals is discussed. Chapter 5 questions what makes a voice memorable, and helps to differentiate between memory for individual voice identities and for the content which was spoken by administering recognition tests both within and across sensory modalities. While the data suggest that experimental manipulation of voice pitch did not influence memory for vocalised stimuli, attractive male voices were better remembered than unattractive voices, independent of pitch manipulation. Memory for cross-modal (textual) content was enhanced by raising the voice pitch of both male and female speakers. I link this pattern of results to the perceived dominance of voices which have been raised and lowered in pitch, and how this might impact how memories are formed and retained. Chapter 6 examines masculinity across visual and auditory sensory modalities using a cross-modal matching task. While participants were able to match voices to muted videos of both male and female speakers at rates above chance, and to static face images of men (but not women), differences in masculinity did not influence observers in their judgements, and voice and face masculinity were not correlated. These results are discussed in terms of the generally-accepted theory that masculinity and femininity in faces and voices communicate the same underlying genetic quality. The biological mechanisms by which vocal and facial masculinity could develop independently are speculated.

The analysis of long-time formant distribution is relatively young but promising discipline of speaker identification. It is a method of mapping the long-term behavior of formants in speech of individual speakers. Frequently encountered problems in practice are bad acoustic quality and very short duration of analyzed recordings. This work aims to present the historical development of forensic phonetics and currently used methods. In the practical part, it deals with the usability of LTF method in forensic practice, especially in recordings containing background noise. It was shown that the noise appreciably affects extracted LTF values and unfortunately the change is not systematic. Therefore, we proposed several methods to compensate the noise in recordings, in order to be able to compare recordings with and without noise. We also investigated the minimum duration of recording, which is necessary for statistical reliability of the resulting values. This boundary is not exact and for each speaker, it is substantially individual. But it is apparent that recordings (vocalic streams) shorter than 15 s often provide incomplete information, wherefore they cannot be recommended for analysis. Keywords: LTF, long-time formant distribution, speaker identification, forensic phonetics, acoustic quality of...

Ce travail entreprend d'évaluer l'évolution de l'acquisition phonologique par des étudiants français des contrastes anglais /ɪ/-/i:/ et /ʊ/-/u:/. Le corpus étudié provient d'enregistrements de conversations spontanées menées avec des étudiants natifs. 12 étudiants, 9 femmes et 3 hommes,ont été suivis lors de 4 sessions espacées chacune d'un intervalle de six mois. L'approche adoptée est résolument quantitative, et agnostique quant aux théories d'acquisition d'une deuxième langue (par exemple Flege 2005, Best 1995,Kuhl 2008). Afin d'estimer les éventuels changements de prononciation, une procédure automatique d'alignement et d'extraction des données acoustiques a été conçue à partir du logiciel PRAAT (Boersma 2001). Dans un premier temps, deux autres logiciels (SPPAS et P2FA, Bigi 2012 et Yuan &Liberman 2008) avaient aligné les transcriptions des enregistrements au phonème près. Plus de 90 000 voyelles ont ainsi été analysées. Les données extraites sont constituées d'informations telles que le nombre de syllabes du mot, de sa transcription acoustique dans le dictionnaire, de la structure syllabique, des phonèmes suivant et précédant la voyelle, de leur lieu et manière d'articulation, de leur appartenance ou non au même mot, mais surtout des relevés formantiques de F0, F1, F2, F3 et F4. Ces relevés formantiques ont été effectués à chaque pourcentage de la durée de la voyelle afin de pouvoir tenir compte des influences des environnements consonantiques sur ces formants. Par ailleurs, des théories telles que le changement spectral inhérent aux voyelles (Nearey & Assmann(1986), Morrison & Nearey (2006), Hillenbrand (2012),Morrison (2012)), ou des méthodes de modélisation du signal telles que la transformation cosinoïdale discrète(Harrington 2010) requièrent que soient relevées les valeurs formantiques des voyelles tout au long de leur durée. Sont successivement étudiées la fiabilité de l'extraction automatique, les distributions statistiques des valeurs formantiques de chaque voyelle et les méthodes de normalisation appropriées aux conversations spontanées. Les différences entre les locuteurs sont ensuite évaluées en analysant tour à tour et après normalisation les changements spectraux, les valeurs formantiques à la moitié de la durée de la voyelle et les transformations cosinoïdales. Les méthodes déployées sont les k plus proches voisins, les analyses discriminantes quadratiques et linéaires, ainsi que les régressions linéaires à effets mixtes. Une conclusion temporaire de ce travail est que l'acquisition du contraste/ɪ/-/i:/ semble plus robuste que celle de /ʊ/-/u:/. / This study undertakes to assess the evolution of the phonological acquisition of the English /ɪ/-/i:/ and /ʊ/-/u:/ contrasts by French students. The corpus is made up of recordings of spontaneous conversations with native speakers. 12 students, 9 females and 3 males, were recorded over 4 sessions in six-month intervals. The approach adopted here is resolutely quantitative, and agnostic with respect to theories of second language acquisition such as Flege's, Best's or Kuhl's. In order to assess the potential changes in pronunciations, an automatic procedure of alignment and extraction has been devised, based on PRAAT (Boersma 2001). Phonemic and word alignments had been carried out with SPPAS (Bigi 2012) and P2FA (Yuan & Liberman 2008) beforehand. More than 90,000 vowels were thus collected and analysed. The extracted data consist of information such as the number of syllables in the word, the transcription of its dictionary pronunciation, the structure of the syllable the vowel appears in, of the preceding and succeeding phonemes, their places and manners of articulation, whether they belong to the same word or not, but also especially of the F0, F1, F2, F3 and F4 formant values. These values were collected at each centile of the duration of the vowel, in order to be able to take into account of the influences of consonantal environments. Besides, theories such as vowel-inherent spectral changes (Nearey & Assmann (1986), Morrison & Nearey (2006), Hillenbrand (2012), Morrison (2012)), and methods of signal modelling such as discrete cosine transforms (Harrington 2010) need formant values all throughout the duration of the vowel. Then the reliability of the automatic procedure, the per-vowel statistical distributions of the formant values, and the normalization methods appropriate to spontaneous speech are studied in turn. Speaker differences are assessed by analysing spectral changes, mid-temporal formant values and discrete cosine transforms with normalized values. The methods resorted to are the k nearest neighbours, linear and quadratic discriminant analyses and linear mixed effects regressions. A temporary conclusion is that the acquisition of the /ɪ/-/i:/ contrast seems more robust than that of the /ʊ/-/u:/ contrast.

This thesis explores, through a number of production andperception studies, the nature of the voice source signal andhow it varies in spoken communication. Research is alsopresented that deals with the techniques and methodologies foranalysing and synthesising the voice source. The main analytictechnique involves interactive inverse filtering for obtainingthe source signal, which is then parameterised to permit thequantification of source characteristics. The parameterisationis carried by means of model matching, using the four-parameterLF model of differentiated glottal flow. The first three analytic studies focus on segmental andsuprasegmental determinants of source variation. As part of theprosodic variation of utterances, focal stress shows for theglottal excitation an enhancement between the stressed voweland the surrounding consonants. At a segmental level, the voicesource characteristics of a vowel show potentially majordifferences as a function of the voiced/voiceless nature of anadjacent stop. Cross-language differences in the extent anddirectionality of the observed effects suggest differentunderlying control strategies in terms of the timing of thelaryngeal and supralaryngeal gestures, as well as in thelaryngeal tensions settings. Different classes of voicedconsonants also show differences in source characteristics:here the differences are likely to be passive consequences ofthe aerodynamic conditions that are inherent to the consonants.Two further analytic studies present voice source correlatesfor six different voice qualities as defined by Laver'sclassification system. Data from stressed and unstressedcontexts clearly show that the transformation from one voicequality to another does not simply involve global changes ofthe source parameters. As well as providing insights into theseaspects of speech production, the analytic studies providequantitative measures useful in technology applications,particularly in speech synthesis. The perceptual experiments use the LF source implementationin the KLSYN88 synthesiser to test some of the analytic resultsand to harness them to explore the paralinguistic dimension ofspeech communication. A study of the perceptual salience ofdifferent parameters associated with breathy voice indicatesthat the source spectral slope is critically important andthat, surprisingly, aspiration noise contributes relativelylittle. Further perceptual tests using stimuli with differentvoice qualities explore the mapping between voice quality andits paralinguistic function of expressing emotion, mood andattitude. The results of these studies highlight the crucialrole of voice quality in expressing affect as well as providingpointers to how it combines withf0for this purpose. The last section of the thesis focuses on the techniquesused for the analysis and synthesis of the source. Asemi-automatic method for inverse filtering is presented, whichis novel in that it optimises the inverse filter by exploitingthe knowledge that is typically used by the experimenter whencarrying out manual interactive inverse filtering. A furtherstudy looks at the properties of the modified LF model in theKLSYN88 synthesiser: it highlights how it differs from thestandard LF model and discusses the implications forsynthesising the glottal source signal from LF model data.Effective and robust source parameterisation for the analysisof voice quality is the topic of the final paper: theeffectiveness of global, amplitude-based, source parameters isexamined across speech tokens with large differences inf0. Additional amplitude-based parameters areproposed to enable a more detailed characterisation of theglottal pulse. <b>Keywords:</b>Voice source dynamics, glottal sourceparameters, source-filter interaction, voice quality,phonation, perception, affect, emotion, mood, attitude,paralinguistic, inverse filtering, knowledge-based, formantsynthesis, LF model, fundamental frequency,f0.

<p>This thesis explores, through a number of production andperception studies, the nature of the voice source signal andhow it varies in spoken communication. Research is alsopresented that deals with the techniques and methodologies foranalysing and synthesising the voice source. The main analytictechnique involves interactive inverse filtering for obtainingthe source signal, which is then parameterised to permit thequantification of source characteristics. The parameterisationis carried by means of model matching, using the four-parameterLF model of differentiated glottal flow.</p><p>The first three analytic studies focus on segmental andsuprasegmental determinants of source variation. As part of theprosodic variation of utterances, focal stress shows for theglottal excitation an enhancement between the stressed voweland the surrounding consonants. At a segmental level, the voicesource characteristics of a vowel show potentially majordifferences as a function of the voiced/voiceless nature of anadjacent stop. Cross-language differences in the extent anddirectionality of the observed effects suggest differentunderlying control strategies in terms of the timing of thelaryngeal and supralaryngeal gestures, as well as in thelaryngeal tensions settings. Different classes of voicedconsonants also show differences in source characteristics:here the differences are likely to be passive consequences ofthe aerodynamic conditions that are inherent to the consonants.Two further analytic studies present voice source correlatesfor six different voice qualities as defined by Laver'sclassification system. Data from stressed and unstressedcontexts clearly show that the transformation from one voicequality to another does not simply involve global changes ofthe source parameters. As well as providing insights into theseaspects of speech production, the analytic studies providequantitative measures useful in technology applications,particularly in speech synthesis.</p><p>The perceptual experiments use the LF source implementationin the KLSYN88 synthesiser to test some of the analytic resultsand to harness them to explore the paralinguistic dimension ofspeech communication. A study of the perceptual salience ofdifferent parameters associated with breathy voice indicatesthat the source spectral slope is critically important andthat, surprisingly, aspiration noise contributes relativelylittle. Further perceptual tests using stimuli with differentvoice qualities explore the mapping between voice quality andits paralinguistic function of expressing emotion, mood andattitude. The results of these studies highlight the crucialrole of voice quality in expressing affect as well as providingpointers to how it combines with<i>f</i>₀for this purpose.</p><p>The last section of the thesis focuses on the techniquesused for the analysis and synthesis of the source. Asemi-automatic method for inverse filtering is presented, whichis novel in that it optimises the inverse filter by exploitingthe knowledge that is typically used by the experimenter whencarrying out manual interactive inverse filtering. A furtherstudy looks at the properties of the modified LF model in theKLSYN88 synthesiser: it highlights how it differs from thestandard LF model and discusses the implications forsynthesising the glottal source signal from LF model data.Effective and robust source parameterisation for the analysisof voice quality is the topic of the final paper: theeffectiveness of global, amplitude-based, source parameters isexamined across speech tokens with large differences in<i>f</i>₀. Additional amplitude-based parameters areproposed to enable a more detailed characterisation of theglottal pulse.</p><p><b>Keywords:</b>Voice source dynamics, glottal sourceparameters, source-filter interaction, voice quality,phonation, perception, affect, emotion, mood, attitude,paralinguistic, inverse filtering, knowledge-based, formantsynthesis, LF model, fundamental frequency,<i>f</i>₀.</p>

Tal och röst styrs av komplicerade processer, där vitt skilda funktioner används i dess produktion och perception. Hur tal och röst uppfattas skiljer sig på flera sätt från den objektiva mätbara akustiska talsignalen. Grundtonens, F0’s, styrka och det man kallar talarformanten är två parametrar som påverkar hur rösten låter. Studien hade som syfte att undersöka om grundtonens styrka och med eller utan talarformant påverkar vilka stimuli otränade röstbedömare tycker bäst om. För att undersöka detta skapades ett syntetiskt /a/ efter formantfrekvenser för svenska vokaler (Fant, 1959), som varierades med utan eller med talarformant och med sju olika grundtonsstyrkor, totalt fjorton stimuli. Tolv kvinnor och åtta män, fick lyssna på /a/:na och skatta dem från det /a/ som de gillade mest till det /a/ som de gillade minst. Studiens frågeställningar bekräftades, variationer av grundtonens styrka och med eller utan talarformant påverkade vilka stimuli otränade röstbedömare föredrog, och män och kvinnor föredrog olika stimuli. De två /a/:na med svagast och det /a/ med starkast grundton, gillades minst av hela gruppen. De fyra /a/:na däremellan tyckte informanterna om ungefär lika mycket. Studerade man var för sig vad män och kvinnor skattade blev resultatet annorlunda. Kvinnor föredrog stimuli med talarformant mer än de utan talarformant, medan män föredrog stimuli med stark grundton. Ytterligare studier kunde vara intressanta att göra, för att undersöka om stimulus egenskaper med avseende på talarformant och grundtonsstyrka har någon effekt på hur tal uppfattas och tolkas. / Speech and voice is governed by complicated processes, where a variety of different functions are used in its production and perception. Speech and voice differs in many ways from the objective measurable acoustic speech signal. The intensity of the fundamental frequency, F0, and what is called the speaker formant are two parameters that affect how voice is perceived. The purpose of the study was to investigate if the varied intensity of F0 and with or without speaker formant affect what stimuli untrained voice assessors like the most. To do so, a synthetic /a/ was created, formed by formant frequencies for Swedish vowels (Fant, 1959), varied with with or without speaker formant, and seven different intensities of the fundamental frequency, creating a total of 14 stimuli. Twelve women and eight men were asked to listen to and grade the stimuli, from the /a/ that was liked the most to the one that was liked the least. The expectations of the study were confirmed, the variation of the intensity of F0 and with or without speaker formant, did affect which stimuli the listeners preferred, and also confirmed that men and women preferred different stimuli. The two /a/’s with the weakest and the /a/ with the strongest intensity of F0, were least liked. The four /a/s with varying intensity of F0 in between, were liked approximately the same. If men and women ratings were studied separately from one another, the result differed. Women preferred stimuli with speaker formant more than the ones without, whereas men more appreciated stimuli with strong intensity of F0. If the study was the be retested and the results would be confirmed, further tests would be of interest to do, to investigate if the differences of preferences affect how speech is perceived and interpreted.

I beskrivningar av somaliska noteras i vissa kontexter en dialektal variation i vokalkvalitet och duration mellan sydsomaliska (benadiri) och nordsomaliska. Modersmålstalare av somaliska bekräftar noterade dialektala skillnader i vokalkvalitet och duration, och anser att det finns en possessivändelse på benadiri eey vilken skiljer sig från den nordsomaliska motsvarigheten ay. Undersökningen syftade till att ta reda på om och på vilket sätt vokalkvalitet och duration varierar, i diftongen ay i de somaliska dialekterna sydsomaliska (benadiri) och nordsomaliska. Studien begränsades till mätning av vokalkvalitet och duration i possessivändelsen -ay. Värden för F1 och F2 i diftongens initialfas, såväl som diftongens duration, mättes i uttal som av modersmålstalare kategoriserats som nordsomaliska respektive sydsomaliska. De uppmätta skillnaderna i vokalkvalitet motsvarade förväntningarna. Genomsnittliga värden för F1 och F2 var lägre respektive högre i samtliga mätgrupper för de uttal som av modersmålstalare klassificerats som sydliga, än för de som klassificerats som nordliga. Det noterades dock att avståndet mellan diftongerna i nordliga och sydliga uttal var betydligt större i ordet aabahay än i hooyaday. Orsaken till detta bör utredas vidare, med fokus på kontextuella skillnader. Endast en obetydlig genomsnittlig durationsskillnad uppmättes. Ett förväntat samband i längdskillnad mellan sydligt och nordligt klassificerade uttal kunde således ej konstateras. / Descriptions of the Somali dialects include a variation in vowel quality and duration, between southern Somali (Benadiri) and northern Somali. Native speakers of Somali confirm noted variations and describe a possessive ending eey in Benadiri, different from the northern Somali equivalent ay. This survey aimed to investigate if, and how, vowel quality and duration vary in the diphthong ay in southern Somali and northern Somali. This study was limited to measuring vowel quality and duration of the possessive ending -ay. Values of F1 and F2 in the initial phase of the diphthong, as well as the duration, were measured in pronunciations, which native speakers have labeled as northern or southern respectively. The measured differences in vowel quality were in line with the expectations. Mean values of F1 and F2 were lower/higher in all measuring groups for the pronunciations labeled as southern, than for those labeled as northern. It was noted, however, that the distance between the diphthongs in northern and southern Somali, was significantly larger in the word aabahay than in hooyaday. The reason for this should be investigated further, focusing on contextual differences. The expected difference in duration between the southern and northern pronunciations could not be found. / <p>Institutionen för lingvistik</p><p>Examensarbete för kandidatexamen 15 hp</p><p>Fonetik</p><p>Kandidatprogram i lingvistik</p><p>Vårterminen 2013</p><p>Handledare: Mattias Heldner</p><p>Examinator: Henrik Liljegren</p><p>English title: Vowel quality and duration of diphthongs in Benadiri and northern Somali </p>

L’objectif de cette thèse est de décrire de manière analytique le spectre du bruit de friction en mettant en évidence l’affiliation des pics spectraux aux cavités du conduit vocal, par le biais de la modélisation acoustique et avec l’aide des données IRM de 7 langues [30 locuteurs]. Les résultats sont les suivants : 1. La dispersion des sibilantes dans l’espace articulatoire dépend du système phonologique [contrastes [+/- antérieur], [+/- distribué], ou les deux]. En français [+/- antérieur], 7 locuteurs], la variation inter-individuelle est importante. 2. Cette variation est due à deux variantes articulatoires du /ʃ/ : (a) plutôt apical, comportant une cavité sublinguale, accompagné de protrusion labiale, et semblable au /ʂ/ polonais ; et [b] palatalisé, mettant en œuvre le bombement du dos de la langue, comparable au /ɕ/ polonais. L’équivalence acoustique des deux variantes est démontrée par une simulation acoustique systématique. 3. En polonais, où la différence articulatoire est phonémique, /ʂ/ est caractérisé par un pic ultra-bas [1,5-1,8 kHz], affilié à la cavité antérieure, d’après la simulation acoustique à l’aide de fonction d’aire réelles de deux locuteurs. 4. Les données articulatoires présentent systématiquement une constriction dentale étroite. D’après la modélisation acoustique, la protrusion labiale aurait comme effet d’abaisser la fréquence d’un formant affilié spécifiquement à la cavité labiale. En somme, la présence de deux constrictions étroites linguale et dentale rend possible le contrôle quasi indépendant d’au moins deux résonances. Cette spécificité garantit aux sibilantes un bruit distinctif qui permet d’expliquer la richesse de leurs inventaires / The aim of this study is to analytically describe the frication noise spectrum in terms of formant affiliation to vocal tract cavities. The high-resolution, teeth-inserted MRI data of sibilants in 7 languages [30 subjects in total] as well as 1D and 3D acoustic modeling are involved. The results are summarized as follows: 1. Sibilants’ dispersion within the articulatory space depends on the language’s phonemic inventory [with contrasts involving [+/- anterior], [+/- distributed], or both features]. A large amount of inter-speaker variation [7 subjects] is observed in French /s/ and /ʃ/ contrasted by [+/- anterior]]. 2. This variation is due to two articulatory variants of the French /ʃ/ : [a] apical, with a sublingual cavity, and protruded lips, like Polish /ʂ/ ; [b] palatalized, with a domed tongue dorsum, like Polish /ɕ/. Systematic acoustic modeling provides evidences about their acoustic equivalence. 3. In Polish, where /ʂ/ and /ɕ/ are contrastive, a super-low peak [1.5 – 1.8 kHz] characterizes the former. The acoustic modeling results using realistic area functions of two subjects show that this peak is affiliated to the front oral cavity. 4. The articulatory data show a systematic narrow constriction at the teeth in all of the examined sibilants. Acoustic modeling shows that lip protrusion results in lowering the formant affiliated specifically to the lip cavity. To conclude, the narrow tongue and teeth constrictions in sibilants allow the speaker to control quasi independently

Cette thèse porte sur l’étude de paramètres acoustiques dans parole fluente chez des locuteurs bègues (SB) et des non-bègues (SNB), tunisiens.Les paramètres acoustiques comparés entre SB et SNB incluent le temps d’établissement du voisement (ou V.O.T), la fréquence du fondamental (F0), des mesures du Jitter et du Shimmer, l’étendue et la direction de la transition du second formant (F2), et également les trois premiers formants (F1, F2 et F3) des trois voyelles /a, i, u/. Les résultats sont en accord avec les études antérieures en ce qui concerne le V.O.T, qui serait aussi plus long chez les bègues américains et français. Concernant les valeurs du F0, des différences significatives entre les deux groupes sont obtenues pour /u/. Les mesures du Jitter et du Shimmer ne montrent pas de différences significatives, contrairement aux résultats recueillis chez les bègues américains où la signification est obtenue pour les mesures du Shimmer. Enfin,en ce qui concerne l’étude des variations formantiques, il y a des tendances sans atteindre la signification pour F1, F2 et F3. Les mesures de F2 sont moins élevées chez les bègues avec quelques résultats significatifs obtenus pour les séquences du type C-u. Le triangle vocalique des trois voyelles /a i u/ chez les enfants bègues tunisiens n’est totalement centralisé contrairement aux triangles obtenus chez les locuteurs bègues français et américains, selon la littérature. / This thesis concerns the comparison of acoustic parameters in fluent speech in Tunisian stutterers’ speakers (SB) and non-stutterers (SNB), Tunisians.The acoustic parameters which are compared between SB and SNB include the Voice Onset Time (VOT), the fundamental frequency (F0), the measurements of jitter and shimmer, the scope and direction of the transition of the second formant (F2), and the first three formants (F1, F2 and F3) of the three vowels /a, i, u/. The results are consistent with previous studies regarding the V.O.T, which has been found also be longer for American and French stutterers. Concerning F0values, significant differences between the two groups are obtained for /u/. Measurements of jitter and shimmer show no significant differences, contrary to the results found from American concerning the shimmer. Finally, as regards the study of formant variations, there are tendencies without reaching significance for F1, F2 and F3. F2 values are lower in stutterers with significant results obtained for sequences of C-u. The vowel triangle of the three vowels /a, u, i/ in Tunisian children who stutter, is not centralized, unlike triangles obtained for French and American stuttering speakers, according to the literature.

In the first part of this master's thesis there is briefly presented the biomechanics of the human voice creation and an overview of the hitherto published computational models of the vocal tract and dissemination of the acoustic waves around the human head. The second part of the thesis deals with the creation of the computational model of a dissemination of the acoustic waves through vocal tract and further into a space around the head during the pronouncing of the Czech vowel /a:/. The vocal tract is excited by a harmonic signal in the place of vocal chords. On the surface of the vocal tract and the part of the head including hair and skin there is defined an acoustic absorption. The dissemination of the acoustic waves in the vocal tract, in the near field around the mouth, in the area around the head and in the points on the cheeks is detailed mapped. The dissemination of the acoustic waves is analyzed in the points where the speech microphones are placed. Acoustic pressure dependence on frequency, transmission functions between defined points and the acoustic pressure amplitudes depending on the distance from the mouth are obtained. In particular, the frequency distortion of the spectra is observed at the points indicated. Furthermore, the radiation impedance in the mouth area is evaluated. The results obtained are compared with the results of the hitherto published experimental measurements and can be used for the exact measurement of human voice or for the frequency correction of the microphones during the scann of the speech and sing placced in the analyzed points.