Electropalatographic Study of Speech Sound Errors in Adults with Acquired Aphasia

Traditionally speech errors in adults with acquired aphasia have been described as either apraxic errors, characteristic of anterior lesions in the cerebral cortex affecting areas such as Broca's area, or phonemic paraphasic errors due to posterior lesions in areas such as Wernicke’s area. However, studies have reported overlap in the descriptions of apraxic and phonemic paraphasic errors despite the assumption that these errors arise from different levels in the speech planning and execution process. For example, phonemic substitutions are associated with both types of error. Part of the problem is due to difficulties in identifying the precise nature and source of the errors which cannot be resolved by auditory perceptual judgements alone. This study investigates, by means of elcctropalatography (EPG), the location and timing of contact patterns produced by ten adults with acquired aphasia. The subjects were variously diagnosed by traditional classification as Broca’s aphasic with or without apraxia, conduction and anomic. These subjects variously demonstrated atypical patterns when compared to ten control speakers such as: increased temporal and/or spatial variability; specific difficulties in the sequencing and timing of two adjacent lingual consonants; and the presence of intrusive lingual/palatal contact patterns. These errors were usually undetected through auditory analysis. The atypical patterns were not associated uniquely with a particular aphasic syndrome but were subject specific and often related to the site of the lesion within the brain, for example, the basal ganglia. Both subjects diagnosed with apraxia of speech and those with phonemic paraphasia produced the EPG patterns noted above. The EPG data provided insights into the nature and origins of errors such as substitutions which were unavailable from auditory-based analysis. Many of these error patterns could be accounted for by modification to Dell’s model of spreading activation (Dell, 1980, 1985, 1986, 1990). The results have important implications for therapeutic intervention since accurate diagnosis is crucial for effective intervention

An Investigation of Coarticulation Resistance in Speech Production Using Ultrasound

Sound segments show considerable influence from neighbouring segments, which is described as being the result of coarticulation. None of the previous reports on coarticulation in vowel-consonant-vowel (VCV) sequences has used ultrasound. One advantage of ultrasound is that it provides information about the shape of most of the midsagittal tongue contour. In this work, ultrasound is employed for studying symmetrical VCV sequences, like /ipi/ and /ubu/, and methods for analysing coarticulation are refined. The use of electropalatography (EPG) in combination with ultrasound is piloted in the study. A unified approach is achieved to describing lingual behaviour during the interaction of different speech sounds, by using the concept of Coarticulation Resistance, which implies that different sounds resist coarticulatory influence to different degrees. The following research questions were investigated: how does the tongue shape change from one segment to the next in symmetrical VCV sequences? Do the vowels influence the consonant? Does the consonant influence the vowels? Is the vocalic influence on the consonant greater than the consonantal influence on the vowels? What are the differences between lingual and non-lingual consonants with respect to lingual coarticulation? Does the syllable/word boundary affect the coarticulatory pattern? Ultrasound data were collected using the QMUC ultrasound system, and in the final experiment some EPG data were also collected. The data were Russian nonsense VCVs with /i/, /u/, /a/ and bilabial stops; English nonsense VhV sequences with /i/, /u/, /a/; English /aka/, /ata/ and /iti/ sequences, forming part of real speech. The results show a significant vowel influence on all intervocalic consonants. Lingual consonants significantly influence their neighbouring vowels. The vocalic influence on the consonants is significantly greater than the consonantal influence on the vowels. Non-lingual consonants exhibit varying coarticulatory patterns. Syllable and word boundary influence on VCV coarticulation is demonstrated. The results are interpreted and discussed in terms of the Coarticulation Resistance theory: Coarticulation Resistance of speech segments varies, depending on segment type, syllable boundary, and language. A method of quantifying Coarticulation Resistance based on ultrasound data is suggested.sub_shsunpub143_ethesesunpu

An Acoustic & Articulatory Analysis of Consonant Sequences across Word Boundaries in Tripolitanian Libyan Arabic

The main goal of this thesis is to provide a description of the articulatory and temporal interaction between stops spanning the word boundary in the four sequence types VC#CV, VC#CCV, VCC#CV, and VCC#CCV in Tripolitanian Libyan Arabic. A general aim of the study is to contribute to the Phonetic description of Libyan Arabic and to provide a better understanding of speech production and the temporal organisation of articulatory gestures. One of the principal objectives of this study is to investigate what effect an increase in the number of stops in a sequence will have on the timing of stop gestures. Furthermore, the study aims to identify the different patterns of gestural coordination and the types of inter-consonantal intervals occurring between stops in the four sequence types. Another aim of the study is to investigate the nature of the resulting inter-consonantal intervals occurring between these stops in order to understand the patterns of epenthesis. Factors affecting gestural coordination such as the order of place of articulation of stops and speech rate are also an objective of this study. Voice assimilation across the word boundary is also investigated in addition to the influence of inter-consonantal intervals on the process. The study adopts Articulatory Phonology as a theoretical framework to carry out the investigations. The data was collected through recordings of participants’ speech and was subjected to EPG and acoustic analysis. Ten native speakers of Tripolitanian Libyan Arabic took part in the acoustic part of the study. Two of the speakers also took part in the EPG part of the study. Results show that the effect of the number of stops in a sequence on gestural timing is not limited to within syllable-initial and final clusters but also spreads across the word boundary. The timing of syllable-final and syllable-initial stops decreases as a result of the increase in the number of stops across the word boundary. The results also show that the timing of syllable-final clusters is more variable than syllable-initial clusters in across word boundary sequences. Different sequences types exhibit different degrees of gestural coordination and epenthesis patterns between adjacent stops. Inter-consonantal intervals occurring as a result of lag durations between adjacent stop gestures fall into two types. The first type are typical of transitional excrescent vowels with a mean duration ranging from 14ms-20ms and their voice values exhibit more variation as a result of the voice context in which they occur. Inter-consonantal intervals of the second type are typical of epenthetic vowels with a mean duration ranging from 43ms-51ms and are usually specified as voiced. The patterns of epenthesis also show that Tripolitanian Libyan Arabic belongs to the VC type of languages where sequences of three stops CCC are broken up by epenthesis occurring between C1 and C2 of the sequence. Statistical tests show a significant effect for order place of articulation on gestural coordination across the word boundary in TLA in the C#C sequence where gestures are more closely coordinated in the coronal-dorsal order. Regressive voice assimilation is more frequent and the voice context of the stops involved plays a major role in determining the direction of voice assimilation spreading. Progressive voice assimilation is limited to the –V+V voice context and whereas regressive assimilation of voicelessness occurs in both. Furthermore, excrescent vowels are found to be transparent to voice assimilation and are dependent on the voicing of the trigger segment. On the other hand, epenthetic vowels block voice assimilation and are more dependent usually specified as voiced

Acoustic and speaker variation in Dutch /n/ and /m/ as a function of phonetic context and syllabic position

In forensic speech science, nasals are often reported to be particularly useful in characterizing speakers because of their low within-speaker and high between-speaker variability. However, empirical acoustic data from nasal consonants indicate that there is a somewhat larger role for the oral cavity on nasal consonant acoustics than is generally predicted by acoustic models. For example, in read speech, nasal consonant acoustics show lingual coarticulation that differs by nasal consonant, and syllabic position also seems to affect realizations of nasal consonants within speakers.  In the current exploratory study, the within and between-speaker variation in the most frequent nasals in Standard Dutch, /n/ and /m/, was investigated. Using 3,695 [n] and 3,291 [m] tokens sampled from 54 speakers’ spontaneous telephone utterances, linear mixed-effects modelling of acoustic-phonetic features showed effects of phonetic context that differed by nasal consonant and by syllabic position. A following speaker-classification test using multinomial logistic regression on the acoustic-phonetic features seems to indicate that nasals displaying larger effects of phonetic context also perform slightly better in speaker classification, although differences were minor. This might be caused by between-speaker variation in the degree and timing of lingual coarticulatory gestures. NWO276-75-010Theoretical and Experimental Linguistic

Rhotics.New Data and Perspectives

This book provides an insight into the patterns of variation and change of rhotics in different languages and from a variety of perspectives. It sheds light on the phonetics, the phonology, the socio-linguistics and the acquisition of /r/-sounds in languages as diverse as Dutch, English, French, German, Greek, Hebrew, Italian, Kuikuro, Malayalam, Romanian, Slovak, Tyrolean and Washili Shingazidja thus contributing to the discussion on the unity and uniqueness of this group of sounds

Prosodic constituent structure and anticipatory pharyngealisation in Libyan Arabic

This study examines anticipatory pharyngealisation (i.e., emphasis) in Libyan Arabic, across a hierarchy of prosodic boundary levels (syllable vs. word vs. phonological phrase vs. intonation phrase ‘IP’) in order to quantify the magnitude, and identify the planned domain of anticipatory pharyngealisation. The acoustic manifestation of pharyngealisation is lowering in the second formant (F2) in pharyngealised contexts compared to their plain cognates. To investigate speech production models of how pharyngealisation is anticipated in advance, F2 measurements were taken at onset, mid and offset points of both vowels (V) in a word-final VCV sequence, in the context [VbV # Emphatic trigger]. The strength of [#], a prosodic boundary, was varied syntactically to manipulate the presumed hierarchical strength of that boundary from zero (where the VbV and the trigger are in the same word) up to an intonational phrase boundary. We expect that the stronger the boundary, the greater the resistance to the spread of pharyngealisation. The duration of the final vowel (i.e., the pre-trigger vowel) was also measured to assess if pharyngealisation magnitude on it and on the first vowel is influenced by the temporal proximity to the emphatic trigger. Results show (1) that within word boundaries pharyngealisation effects are present on both vowels, and (2) there are effects of pharyngealisation on the final vowel, i.e. the pre-trigger across word and phrase boundaries, and (3) there is no evidence of pharyngealisation across an IP boundary. An examination of the pre-trigger vowel + pause duration suggests that the lack of coarticulatory effects on the final vowel, i.e., pre-trigger vowel, across an IP boundary may be due to the temporal distance from the trigger: all tokens in this condition had a pre-trigger pause. For word and phrase boundary conditions, F2 was higher the greater the temporal distance from the pharyngealised trigger. These results suggest that anticipatory pharyngealisation is qualitatively different within the word as compared to across word boundaries. More clearly, the magnitude of pharyngealisation is categorical within word boundaries, and gradient across prosodic boundaries higher than the word. These findings suggest that pharyngealisation within the word is phonological, whereas across word boundaries it is primarily a phonetic process, conditioned by the temporal proximity to the pharyngealised trigger. Results also show that the planned domain of [pharyngealisation] is the word. However, additional phonetic pharyngealisation effects can extend across word boundaries as a result of coarticulation

Experimental phonetic study of the timing of voicing in English obstruents

The treatment given to the timing of voicing in three areas of phonetic research -- phonetic taxonomy, speech production modelling, and speech synthesis -- Is considered in the light of an acoustic study of the timing of voicing in British English obstruents. In each case, it is found to be deficient. The underlying cause is the difficulty in applying a rigid segmental approach to an aspect of speech production characterised by important inter-articulator asynchronies, coupled to the limited quantitative data available concerning the systematic properties of the timing of voicing in languages. It is argued that the categories and labels used to describe the timing of voicing In obstruents are Inadequate for fulfilling the descriptive goals of phonetic theory. One possible alternative descriptive strategy is proposed, based on incorporating aspects of the parametric organisation of speech into the descriptive framework. Within the domain of speech production modelling, no satisfactory account has been given of fine-grained variability of the timing of voicing not capable of explanation in terms of general properties of motor programming and utterance execution. The experimental results support claims In the literature that the phonetic control of an utterance may be somewhat less abstract than has been suggestdd in some previous reports. A schematic outline is given, of one way in which the timing of voicing could be controlled in speech production. The success of a speech synthesis-by-rule system depends to a great extent on a comprehensive encoding of the systematic phonetic characteristics of the target language. Only limited success has been achieved in the past thirty years. A set of rules is proposed for generating more naturalistic patterns of voicing in obstruents, reflecting those observed in the experimental component of this study. Consideration Is given to strategies for evaluating the effect of fine-grained phonetic rules In speech synthesis