Tongue/palate contact for the production of /s/ and /z/

Productions of /s/ and /z/ by ten adult speakers were investigated using the electropalatograph (EPG). The participants, ten speech researchers who spoke English as their first language, recorded productions of /s/ and /z/ in nonsense and real words. The maximum contact frame was used as the point of reference to compare tongue/palate contact for each production. Each speaker had alveolar contact, lateral bracing and most had a midline groove for both /s/ and /z/; however, the array of contacted electrodes was unique for each speaker. The groove widths and lengths ranged from 0–3 electrodes. There was significantly greater alveolar tongue/palate contact for /z/ compared to /s/ in word‐initial position, but not in word‐final position for the following measures: alveolar palatal contact, medial groove width, medial groove length. However, when measures of total palate contact and centre of gravity were considered, there was a complex interaction between the phonemes /s/ and /z/, coarticulation with the vowel, word position, and word context (real and nonsense words).     

Tongue/palate contact for the production of /s/ and /z/

Productions of /s/ and /z/ by ten adult speakers were investigated using the electropalatograph (EPG). The participants, ten speech researchers who spoke English as their first language, recorded productions of /s/ and /z/ in nonsense and real words. The maximum contact frame was used as the point of reference to compare tongue/palate contact for each production. Each speaker had alveolar contact, lateral bracing and most had a midline groove for both /s/ and /z/; however, the array of contacted electrodes was unique for each speaker. The groove widths and lengths ranged from 0-3 electrodes. There was significantly greater alveolar tongue/palate contact for /z/ compared to /s/ in word-initial position, but not in word-final position for the following measures: alveolar palatal contact, medial groove width, medial groove length. However, when measures of total palate contact and centre of gravity were considered, there was a complex interaction between the phonemes /s/ and /z/, coarticulation with the vowel, word position, and word context (real and nonsense words).     

Speech-language pathologists' knowledge of tongue/palate contact for consonants

Speech-language pathologists (SLPs) rely on knowledge of tongue placement to assess and provide intervention. A total of 175 SLPs who worked with children with speech sound disorders (SSDs) drew coronal diagrams of tongue/palate contact for 24 English consonants. Comparisons were made between their responses and typical English-speaking adults' contact established by electropalatography (EPG). SLPs were most accurate for consonants with no contact (h, p, f), then velar consonants (g, k, ng). The remaining consonants were rarely accurate (from most to least accurate: l, t, r, z, n, sh, s, zh, y, v, th(voiceless), d, m, b, w, th(voiced), ch, j). SLPs demonstrated good knowledge of contact along the midline, but poor knowledge of contact along lateral margins of the palate. Importantly, SLPs did not show awareness of: lateral bracing ('horseshoe' contact) for alveolar consonants (t, d, n, s, z); the groove for s, z, sh, zh; or posterior lateral contact for most other consonants. Accuracy was not influenced by the following: length of time as SLP, location of SLP training, location of current workplace, proportion of caseload with SSD or childhood apraxia of speech, amount of time spent reading, or exposure to EPG. Awareness of coronal tongue placement for consonant production needs targeting in SLP education.     

Speech–language pathologists’ knowledge of tongue/palate contact for consonants

Speech–language pathologists (SLPs) rely on knowledge of tongue placement to assess and provide intervention. A total of 175 SLPs who worked with children with speech sound disorders (SSDs) drew coronal diagrams of tongue/palate contact for 24 English consonants. Comparisons were made between their responses and typical English-speaking adults’ contact established by electropalatography (EPG). SLPs were most accurate for consonants with no contact (h, p, f), then velar consonants (g, k, ng). The remaining consonants were rarely accurate (from most to least accurate: l, t, r, z, n, sh, s, zh, y, v, th(voiceless), d, m, b, w, th(voiced), ch, j). SLPs demonstrated good knowledge of contact along the midline, but poor knowledge of contact along lateral margins of the palate. Importantly, SLPs did not show awareness of: lateral bracing (‘horseshoe’ contact) for alveolar consonants (t, d, n, s, z); the groove for s, z, sh, zh; or posterior lateral contact for most other consonants. Accuracy was not influenced by the following: length of time as SLP, location of SLP training, location of current workplace, proportion of caseload with SSD or childhood apraxia of speech, amount of time spent reading, or exposure to EPG. Awareness of coronal tongue placement for consonant production needs targeting in SLP education.     

Voicing judgements by chinchillas trained with a reward paradigm

Experiments were performed to replicate and extend previous findings of similar categorization of voiced/voiceless consonant–vowel (CV) syllables by humans and chinchillas. A reward paradigm was applied to the question of how stimulus range affects the voice-onset-time (VOT) corresponding to the voiced/voiceless category boundary. Each of four adult chinchillas and four human subjects identified synthetic CV syllables as voiced (/ba/, /da/, /ga/) or voiceless (/pa/, /ta/, /ka/) using voiceless standards of either 80 or 120 ms. In both humans and animals, extending the VOT range from 80 to 120 ms shifted category boundaries to longer VOTs, but to a different extent across listeners. Control experiments suggested that listeners were attending to different phonetic cues in a manner that depended on the listener, rather than on species. The results are interpreted in terms of similar contextual effects and use of multiple phonetic cues to voicing in humans and animals.     

Sibilant production in Hebrew-speaking adults: Apical versus laminal

The Hebrew IPA charts describe the sibilants /s, z/ as ‘alveolar fricatives’, where the place of articulation on the palate is the alveolar ridge. The point of constriction on the tongue is not defined – apical (tip) or laminal (blade). Usually, speech and language pathologists (SLPs) use the apical placement in Hebrew articulation therapy. Some researchers and SLPs suggested that acceptable /s, z/ could be also produced with the laminal placement (i.e. the tip of the tongue approximating the lower incisors). The present study focused at the clinical level, attempting to determine the prevalence of these alternative points of constriction on the tongue for /s/ and /z/ in three different samples of Hebrew-speaking young adults (total n = 242), with typical articulation. Around 60% of the participants reported using the laminal position, regardless of several speaker-related variables (e.g. tongue-thrust swallowing, gender). Laminal production was more common in /s/ (than /z/), coda (than onset) position of the sibilant, mono- (than di-) syllabic words, and with non-alveolar (than alveolar) adjacent consonants. Experiment 3 revealed no acoustical differences between apical and laminal productions of /s/ and of /z/. From a clinical perspective, we wish to raise the awareness of SLPs to the prevalence of the two placements when treating Hebrew speakers, noting that tongue placements were highly correlated across sibilants. Finally, we recommend adopting a client-centred practice, where tongue placement is matched to the client. We further recommend selecting targets for intervention based on our findings, and separating between different prosodic positions in treatment.     

Voice-onset time in younger and older French-speaking Canadians

Voice-onset time (VOT) production was measured in a group of 10 younger (average age 24 years) and 10 older French-speaking Canadian males (average age 67 years). Each subject produced 90 syllables (15 VOT measures for each of the stop consonants /p/, /t/, /k/ and /b/, /d/, /g/ in a CV environment). There was a significant interaction of age and voicing—that is the younger subjects had significantly more average difference in VOT between voiced and voiceless stops. Standard deviations were significantly greater in the older subjects for the voiced consonants and smaller for the voiceless consonants when compared to those for the younger subjects. These results are discussed in the light of the literature on the effects of ageing on VOT production.     

Voice onset time in Friedreich dysarthria]

This study concerned VOT measurements of voiced and voiceless occlusives produced in a sample of spontaneous language from 16 French speakers with Friedreich's ataxia. The results revealed that average VOT values were positive for voiceless stops and negative for voiced stops and thus were in agreement with published data for French. There was, however, a reduction of the difference between the two voicing categories and large between-subject variability. The factors that could have contributed to the increase in between-subject variability and to the reduction of the difference between the two categories are discussed. Finally, some leads for the use of VOT in the therapeutic process are proposed.     

Treating control of voicing in apraxia of speech with variable practice

Background: Apraxia of speech (AOS) is generally considered a phonetic‐motoric disorder. As such, it is reasonable to draw on the motor learning literature to develop interventions for improving articulation. The often cited problem of impaired voicing control is used to test the application of a variable practice approach to training skilled movements in AOS. It is predicted that variable practice—practising a behaviour over a range of possible values or contexts—increases accuracy and stability of a trained behaviour.

Aims: The aims of the study were to test the influence of variable practice conditions on acquisition and long‐term maintenance of voiced and voiceless phonemes in words at the phrase/sentence level as well as on generalisation of treatment effects to phonemes of same and different manner. The protocol was tested on two individuals with moderate AOS, one of whom exhibited a concomitant moderate aphasia.

Methods & Procedures: A single subject multiple baseline across‐subjects design was used to examine efficacy of treatment for improving control of voicing for three fricative/affricate phonemes (Participant 1) or three plosive phonemes (Participant 2). The training sets included two voiced phonemes and one voiceless phoneme, each presented in the initial position of 10 different words. This provided a range of voice onset times and a range of phonetic contexts for each target phoneme, thus providing the variable practice. The inclusion of a voiceless phoneme that was produced at a high level of accuracy during baseline was hypothesised to reduce the chance of overgeneralisation from voiced to voiceless phoneme production.

Outcomes & Results: Consistent with predictions, participants demonstrated improved production of trained voiced phonemes and generalisation of treatment effects to untrained phonemes of same manner only. These effects were maintained up to 3 months post‐treatment. Results support training multiple fricatives or plosives in parallel in a variety of phonetic contexts (i.e., variable practice) as well as including a combination of voiced and voiceless phonemes in treatment to ensure maintenance of accurate voiceless phoneme production.

Conclusions: Results from two participants, varying in overall communication impairment severity, provide promising evidence that a variable practice approach to retraining speech behaviours in AOS is effective. Specifically, this approach resulted in long‐term maintenance of treatment effects and generalisation of treatment effects to untrained phonemes within manner class. Just as importantly, it did not result in overgeneralisation of voicing to voiceless phonemes. Further testing is required before recommending general clinical application.     

Patterns of laryngeal apraxia in two patients with Broca's aphasia

In this study the transillumination technique was applied to the study of laryngeal movements during speaking in two Broca's aphasics with apraxia of speech. In particular, laryngeal adductory and abductory gestures in the production of voiced and voiceless obstruents were analysed. The two patients presented disturbances concerning movement shape, amplitude, and timing. Patient 1 had particular problems in the initiation of laryngeal adduction. These observations are compared to the patients' clinical patterns of apraxic speech and are discussed in the light of earlier studies of apraxic speech.     

The acquisition of the voicing contrast in word-initial bilabial and alveolar stops – Atypical data from Hungarian

The present study aims to investigate, through acoustic analysis, the acquisition of voicing contrast in Hungarian word-initial bilabial and alveolar stops (p/b and t/d) produced by 15 children with primary language disorders between 5;6 and 7;7 years of age. Data collection was based on a picture-naming task involving at least four different pictures for each segment tested. The elicited data were audio-recorded and then evaluated in terms of the proportion of pre-voiced stops per target category, the duration of voice onset time (VOT), and the presence of other phonetic features. The results revealed that, while all target voiceless stops are produced without pre-voicing, there is a bimodal distribution of VOTs for target voiced categories. Regarding the duration of VOTs, accurate realisations show average VOTs of immature values, and no sub-phonemic level differences were revealed in the distribution of VOTs for inaccurate realisations. Furthermore, voiceless realisations present frequently double/multiple release bursts. Findings are discussed in relation to a study on VOT distribution in the speech of typically developing children and to suggestions for further investigations.     

Development of voice onset time in standard-Greek and Cypriot-Greek-speaking preschoolers

The current investigation examined the development of voice onset time (VOT) in Standard-Greek (SG) and Cypriot-Greek (CG)-speaking children at age levels 2;0–2;5, 2;6–2;11, 3;0–3;5, and 3;6–4;0 years. SG presents with a two-way voicing contrast (voiced and voiceless unaspirated stops) whereas CG is a three-way contrast dialect containing voiceless unaspirated, voiceless aspirated, and pre-voiced stops. A cross-sectional design was used. The main goals were: (1) to determine the age at which Greek and Cypriot Greek children acquire voicing contrasts, and (2) to examine the mechanism used during the process of acquisition. Stimuli included pseudo words in minimal pair contrasts differing in stop voicing (e.g. [′gaga] vs [′kaka]). Children were taught the target words using fast mapping procedures. Each member within a word pair referred to an unfamiliar object. Audio-recorded samples were analysed from wide-band spectrograms. Results indicated a greater overall variation of voicing patterns for children than adults, in both Greek and Cypriot VOT contrasts. Greek children acquired consistent pre-voicing and short lag aspiration patterns very early on, achieving adult values for VOT contrasts for alveolar and for velar places of articulation as early as 2;0–2;5 years old. On the contrary, a developmental lag in the acquisition of voicing contrasts was noted for Cypriot children as compared to the Greek counterparts. Accounts about the developmental differences among Greek and Cypriot children with respect to the adult VOT contrasts are discussed.     

Efficacy of speech intervention using electropalatography with a cochlear implant user

Electropalatography (EPG) has become relatively well established as a safe and convenient technique for use in the assessment, diagnosis and treatment of children and adults with articulation disorders. EPG's wide applicability is reflected in the range of different cases that has been researched in recent years. Some research has been carried out using EPG therapy for deaf individuals who use hearing aids, however there are no similar studies for cochlear implant users. The purpose of this single case study is to explore the technique of EPG as a therapeutic intervention to treat voiceless velar stop consonant sound production in a deaf child cochlear implant user. EPG therapy was offered as a last resort when traditional therapy failed to achieve specific changes. During therapy, a list of familiar words was practised, using the visual feedback provided by EPG. The client's articulation was assessed using objective (EPG printouts) and subjective (listener ratings) measures at four assessment points. Changes were found to be statistically significant. Generalization of the newly‐acquired skills to untaught words containing voiceless velars was also observed. The results are discussed in the broader context of implications of this type of therapy with deaf clients.     

Temporal control in the voicing contrast: Evidence from surgery-related apraxia of speech

ABSTRACT

The goal of this study was to investigate the phonetic realisation of the voicing feature in two tumour resection-related Spanish speakers with apraxia of speech. Temporal parameters related to the phonological contrast of voicing in Spanish have been analysed for intervocalic voiced and voiceless obstruents embedded in isolated words and nonwords, and compared with data collected from healthy speakers. Results indicate that in devoiced productions, where VOT values fitted the ‘voiceless stops’ category, vowel duration values matched those of voiced stops and suggested the preservation of contextual voicing cues. An attempt at preserving a consonant/vowel duration ratio consistent with aerodynamic predictions for voicing contrast has been observed in apraxic correct production as well as in devoicing errors, but not in the control group, which could be interpreted as a compensatory mechanism.     

Stop voicing in thai after unilateral brain damage

Abstract

Word-initial bilabial stops (/b p ph/), alveolar stops (/d t th/), and velar stops (/k kh/) in Thai were produced by 20 normal adults (10 young, 10 old), 12 non-aphasic patients with unilateral right hemisphere lesions, and 17 aphasic patients with unilateral left hemisphere lesions (nine fluent, eight non-fluent). Voice onset time (VOT) was measured from broad-band spectrograms. Relative frequency distributions of VOT values indicated minimal or no overlap between homorganic stop consonants for normal speakers, only sporadic occurrences of overlap for right hemisphere speakers, slightly more overlap for left fluent speakers, and even more overlap for left non-fluent speakers. By group, mean VOTs of homorganic stop consonants differed for all groups except /d t/ for the left non-fluent. By voicing category, mean VOTs of /b d/ for the left non-fluent group were shorter than those of other groups, and mean VOT of /k/ was longer than those of other groups. Mean VOTs of /ph th kh/ for the old normal group were shorter than those of the young normal and left hemisphere groups. Variability in VOT for the left non-fluent group was larger than that for normal groups only. Though not satistically significant, the left fluent and right hemisphere groups were also more variable in VOT production than normal speakers. Across groups, variability in VOT was smaller for voiceless unaspirated stops, larger for voiced unaspirated, and intermediate for voiceless aspirated stops. Findings are discussed in relation to issues pertaining to phonetic deficits in non-fluent aphasic patients.     

Early phonetic development in typically developing children: A longitudinal investigation from Cypriot-Greek child data

The current longitudinal study examined the acquisition of consonantal singleton segments in Cypriot-Greek. The study’s aims were: (a) to determine the acquisition of segments for manner and place of articulation as a function of age and word position, (b) to provide preliminary normative data, and (c) to further support the cross-linguistic data pool regarding developmental phonology patterns. Participants were 14 Cypriot-Greek speaking typically developing toddlers, examined at ages 24, 28, 32 and 36 months. Spontaneously produced and elicited glossable utterances were used in constructing each child’s inventory. Findings revealed an increase of segmental acquisition across all age levels. Group trend analysis for manner and place of articulation indicated bilabial and alveolar stops and nasals to be among the earlier segments to develop. A word medial position advantage was also evident. The findings are discussed in terms of phonological universals and language-specific factors. Implications for early evidence-based phonetic assessment are discussed.     

Efficacy of speech intervention using electropalatography with a cochlear implant user

Electropalatography (EPG) has become relatively well established as a safe and convenient technique for use in the assessment, diagnosis and treatment of children and adults with articulation disorders. EPG's wide applicability is reflected in the range of different cases that has been researched in recent years. Some research has been carried out using EPG therapy for deaf individuals who use hearing aids, however there are no similar studies for cochlear implant users. The purpose of this single case study is to explore the technique of EPG as a therapeutic intervention to treat voiceless velar stop consonant sound production in a deaf child cochlear implant user. EPG therapy was offered as a last resort when traditional therapy failed to achieve specific changes. During therapy, a list of familiar words was practised, using the visual feedback provided by EPG. The client's articulation was assessed using objective (EPG printouts) and subjective (listener ratings) measures at four assessment points. Changes were found to be statistically significant. Generalization of the newly-acquired skills to untaught words containing voiceless velars was also observed. The results are discussed in the broader context of implications of this type of therapy with deaf clients.