Temporal organization of syllables in paced and unpaced speech in children and adolescents who stutter.

PURPOSE: Speaking with an external rhythm has a tremendous fluency-enhancing effect in people who stutter. The aim of the present study is to examine whether syllabic timing related to articulatory timing (c-center) would differ between children and adolescents who stutter and a matched control group in an unpaced vs. a paced condition. METHODS: We recorded 48 German-speaking children and adolescents who stutter and a matched control group reading monosyllabic words with and without a metronome (unpaced and paced condition). Analyses were conducted on four minimal pairs that differed in onset complexity (simple vs. complex). The following acoustic correlates of a c-center effect were analyzed: vowel and consonant compression, acoustic intervals (time from c-center, left-edge, and right-edge to an anchor-point), and relative standard deviations of these intervals. RESULTS: Both groups show acoustic correlates of a c-center effect (consonant compression, vowel compression, c-center organization, and more stable c-center intervals), independently of condition. However, the group who stutters had a more pronounced consonant compression effect. The metronome did not significantly affect syllabic organization but interval stability improved in the paced condition in both groups. CONCLUSION: Children and adolescents who stutter and matched controls have a similar syllable organization, related to articulatory timing, regardless of paced or unpaced speech. However, consonant onset timing differs between the group who stutters and the control group; this is a promising basis for conducting an articulatory study in which articulatory (gestural) timing can be examined in more detail.

Vowel height and velum position in German: Insights from a real-time magnetic resonance imaging study.

Velum position was analysed as a function of vowel height in German tense and lax vowels preceding a nasal or oral consonant. Findings from previous research suggest an interdependence between vowel height and the degree of velum lowering, with a higher velum during high vowels and a more lowered velum during low vowels. In the current study, data were presented from 33 native speakers of Standard German who were measured via non-invasive high quality real-time magnetic resonance imaging. The focus was on exploring the spatiotemporal extent of velum lowering in tense and lax /a, i, o, ø/, which was done by analysing velum movement trajectories over the course of VN and VC sequences in CVNV and CVCV sequences by means of functional principal component analysis. Analyses focused on the impact of the vowel category and vowel tenseness. Data indicated that not only the position of the velum was affected by these factors but also the timing of velum closure. Moreover, it is argued that the effect of vowel height was to be better interpreted in terms of the physiological constriction location of vowels, i.e., the specific tongue position rather than phonetic vowel height.

Temporal malleability to auditory feedback perturbation is modulated by rhythmic abilities and auditory acuity.

Auditory feedback perturbation studies have indicated a link between feedback and feedforward mechanisms in speech production when participants compensate for applied shifts. In spectral perturbation studies, speakers with a higher perceptual auditory acuity typically compensate more than individuals with lower acuity. However, the reaction to feedback perturbation is unlikely to be merely a matter of perceptual acuity but also affected by the prediction and production of precise motor action. This interplay between prediction, perception, and motor execution seems to be crucial for the timing of speech and non-speech motor actions. In this study, to examine the relationship between the responses to temporally perturbed auditory feedback and rhythmic abilities, we tested 45 adult speakers on the one hand with a temporal auditory feedback perturbation paradigm, and on the other hand with rhythm perception and production tasks. The perturbation tasks temporally stretched and compressed segments (onset + vowel or vowel + coda) in fluent speech in real-time. This technique sheds light on the temporal representation and the production flexibility of timing mechanisms in fluent speech with respect to the structure of the syllable. The perception tasks contained staircase paradigms capturing duration discrimination abilities and beat-alignment judgments. The rhythm production tasks consisted of finger tapping tasks taken from the BAASTA tapping battery and additional speech tapping tasks. We found that both auditory acuity and motor stability in finger tapping affected responses to temporal auditory feedback perturbation. In general, speakers with higher auditory acuity and higher motor variability compensated more. However, we observed a different weighting of auditory acuity and motor stability dependent on the prosodic structure of the perturbed sequence and the nature of the response as purely online or adaptive. These findings shed light on the interplay of phonological structure with feedback and feedforward integration for timing mechanisms in speech.

Reading Fluency in Children and Adolescents Who Stutter.

Speech fluency is a major challenge for young persons who stutter. Reading aloud, in particular, puts high demands on fluency, not only regarding online text decoding and articulation, but also in terms of prosodic performance. A written text has to be segmented into a number of prosodic phrases with appropriate breaks. The present study examines to what extent reading fluency (decoding ability, articulation rate, and prosodic phrasing) may be altered in children (9-12 years) and adolescents (13-17 years) who stutter compared to matched control participants. Read speech of 52 children and adolescents who do and do not stutter was analyzed. Children and adolescents who stutter did not differ from their matched control groups regarding reading accuracy and articulation rate. However, children who stutter produced shorter pauses than their matched peers. Results on prosodic phrasing showed that children who stutter produced more major phrases than the control group and more intermediate phrases than adolescents who stutter. Participants who stutter also displayed a higher number of breath pauses. Generally, the number of disfluencies during reading was related to slower articulation rates and more prosodic boundaries. Furthermore, we found age-related changes in general measures of reading fluency (decoding ability and articulation rate), as well as the overall strength of prosodic boundaries and number of breath pauses. This study provides evidence for developmental stages in prosodic phrasing as well as for alterations in reading fluency in children who stutter.

Compensation to real-time temporal auditory feedback perturbation depends on syllable position.

Auditory feedback perturbations involving spectral shifts indicated a crucial contribution of auditory feedback to planning and execution of speech. However, much less is known about the contribution of auditory feedback with respect to temporal properties of speech. The current study aimed at providing insight into the representation of temporal properties of speech and the relevance of auditory feedback for speech timing. Real-time auditory feedback perturbations were applied in the temporal domain, viz., stretching and compressing of consonant-consonant-vowel (CCV) durations in onset + nucleus vs vowel-consonant-consonant (VCC) durations in nucleus + coda. Since CCV forms a gesturally more cohesive and stable structure than VCC, greater articulatory adjustments to nucleus + coda (VCC) perturbation were expected. The results show that speakers compensate for focal temporal feedback alterations. Responses to VCC perturbation were greater than to CCV perturbation, suggesting less deformability of onsets when confronted with temporally perturbed auditory feedback. Further, responses to CCV perturbation rather reflected within-trial reactive compensation, whereas VCC compensation was more pronounced and indicative of adaptive behavior. Accordingly, planning and execution of temporal properties of speech are indeed guided by auditory feedback, but the precise nature of the reaction to perturbations is linked to the structural position in the syllable and the associated feedforward timing strategies.

Mixed modeling for irregularly sampled and correlated functional data: Speech science applications.

The speech sciences often employ complex experimental designs requiring models with multiple covariates and crossed random effects. For curve-like data such as time-varying signals, single-time-point feature extraction is commonly used as data reduction technique to make the data amenable to statistical hypothesis testing, thereby discarding a wealth of information. The present paper discusses the application of functional linear mixed models, a functional analogue to linear mixed models. This type of model allows for the holistic evaluation of curve dynamics for data with complex correlation structures due to repeated measures on subjects and stimulus items. The nonparametric, spline-based estimation technique allows for correlated functional data to be observed irregularly, or even sparsely. This means that information on variation in the temporal domain is preserved. Functional principal component analysis is used for parsimonious data representation and variance decomposition. The basic functionality and usage of the model is illustrated based on several case studies with different data types and experimental designs. The statistical method is broadly applicable to any types of data that consist of groups of curves, whether they are articulatory or acoustic time series data, or generally any types of data suitably modeled based on penalized splines.

A Cross-Language Study of Laryngeal-Oral Coordination Across Varying Prosodic and Syllable-Structure Conditions.

Purpose: The purpose of this study is to use prosodic and syllable-structure variation to probe the underlying representation of laryngeal kinematics in languages traditionally considered to differ in voicing typology (German vs. Dutch and French). Method: Transillumination and videofiberendoscopic filming were used to investigate the devoicing gesture in German, Dutch, and French for material that compared, first, a strong versus weak prosodic condition and, second, singletons versus clusters (stop + /r/ and /l/). Results: The results showed strengthening of the devoicing gesture in the strong prosodic condition and in the segmental context stop + /r/ for German and French but not for Dutch. In terms of timing (duration of oral occlusion, voice onset time, timing of peak glottal opening relative to stop release), French was intermediate between German and Dutch. Conclusions: (a) The representation of French voiceless plosives requires an active specification for glottal spreading just as in German. (b) Static features are not well suited to capturing cross-language differences in voicing typology and changes in voicing specification over time.

Temporal variability in sung productions of adolescents who stutter.

UNLABELLED: Singing has long been used as a technique to enhance and reeducate temporal aspects of articulation in speech disorders. In the present study, differences in temporal structure of sung versus spoken speech were investigated in stuttering. In particular, the question was examined if singing helps to reduce VOT variability of voiceless plosives, which would indicate enhanced temporal coordination of oral and laryngeal processes. Eight German adolescents who stutter and eight typically fluent peers repeatedly spoke and sang a simple German congratulation formula in which a disyllabic target word (e.g., /'ki:ta/) was repeated five times. Every trial, the first syllable of the word was varied starting equally often with one of the three voiceless German stops /p/, /t/, /k/. Acoustic analyses showed that mean VOT and stop gap duration reduced during singing compared to speaking while mean vowel and utterance duration was prolonged in singing in both groups. Importantly, adolescents who stutter significantly reduced VOT variability (measured as the Coefficient of Variation) during sung productions compared to speaking in word-initial stressed positions while the control group showed a slight increase in VOT variability. However, in unstressed syllables, VOT variability increased in both adolescents who do and do not stutter from speech to song. In addition, vowel and utterance durational variability decreased in both groups, yet, adolescents who stutter were still more variable in utterance duration independent of the form of vocalization. These findings shed new light on how singing alters temporal structure and in particular, the coordination of laryngeal-oral timing in stuttering. Future perspectives for investigating how rhythmic aspects could aid the management of fluent speech in stuttering are discussed. LEARNING OUTCOMES: Readers will be able to describe (1) current perspectives on singing and its effects on articulation and fluency in stuttering and (2) acoustic parameters such as VOT variability which indicate the efficiency of control and coordination of laryngeal-oral movements. They will understand and be able to discuss (3) how singing reduces temporal variability in the productions of adolescents who do and do not stutter and 4) how this is linked to altered articulatory patterns in singing as well as to its rhythmic structure.

Articulatory and Acoustic Characteristics of German Fricative Clusters.

BACKGROUND: We investigate the articulatory-acoustic relationship in German fricative sequences. We pursue the possibility that /f/#sibilant and /s#ʃ/ sequences are in principle subject to articulatory overlap in a similar fashion, yet due to independent articulators being involved, there is a significant difference in the acoustic consequences. We also investigate the role of vowel context and stress. METHODS: We recorded electropalatographic and acoustic data from 9 native speakers of German. RESULTS: Results are compatible with the hypothesis that the temporal organization of fricative clusters is globally independent of cluster type with differences between clusters appearing mainly in degree. Articulatory overlap may be obscured acoustically by a labiodental constriction, similarly to what has been reported for stops. CONCLUSION: Our data suggest that similar principles of articulatory coordination underlie German fricative clusters independently of their segmental composition. The general auditory-acoustic patterning of the fricative sequences can be predicted by taking into account that aerodynamicacoustic consequences of gestural overlap may vary as a function of the articulators involved. We discuss possible sources for differences in degrees of overlap and place our results in the context of previously reported asymmetries among the fricatives in regressive place assimilation.

Articulatory overlap as a function of voicing in French and German consonant clusters.

The effects of laryngeal specification on the timing of supra-laryngeal articulations have so far received little attention. Previous research has shown that German-but not French-mixed-voicing clusters are produced with less articulatory overlap than phonologically fully voiced clusters. Articulatory and acoustic data of labial and velar stops as simple onsets and in stop + /l/ clusters are examined to probe the causes for this cross-linguistic difference in the light of the different voicing implementations of French and German. The absence of overlap in German mixed-voicing clusters is attributed to the requirement of a time slot for the stop's aspiration phase. Since French does not commonly have aspirated stops, French clusters are expected to pattern with the voiced German clusters. The results confirm that voicing patterns established for simple onsets in the literature in terms of voice onset time of both German and French also obtain in clusters. Furthermore, the data show that contrary to the expectations French clusters pattern with German mixed-voicing clusters. This low degree of overlap in both voiceless and voiced French clusters indicates that overlap is restricted by aerodynamic requirements which result from the implementations of the voicing contrast.

The influence of auditory acuity on acoustic variability and the use of motor equivalence during adaptation to a perturbation.

PURPOSE: The aim of this study was to relate speakers' auditory acuity for the sibilant contrast, their use of motor equivalent trading relationships in producing the sibilant /∫/, and their produced acoustic distance between the sibilants /s/ and /∫/. Specifically, the study tested the hypotheses that during adaptation to a perturbation of vocal-tract shape, high-acuity speakers use motor equivalence strategies to a greater extent than do low-acuity speakers in order to reach their smaller phonemic goal regions, and that high-acuity speakers produce greater acoustic distance between 2 sibilant phonemes than do low-acuity speakers. METHOD: Articulographic data from 7 German speakers adapting to a perturbation were analyzed for the use of motor equivalence. The speakers' produced acoustic distance between /s/ and /∫/ was calculated. Auditory acuity was assessed for the same speakers. RESULTS: High-acuity speakers used motor equivalence to a greater extent when adapting to a perturbation than did low-acuity speakers. Additionally, high-acuity speakers produced greater acoustic contrasts than did low-acuity-speakers. It was observed that speech rate had an influence on the use of motor equivalence: Slow speakers used motor equivalence to a lesser degree than did fast speakers. CONCLUSION: These results provide support for the mutual interdependence of speech perception and production.

Jaw and order.

It is well-accepted that the jaw plays an active role in influencing vowel height. The general aim of the current study is to further investigate the extent to which the jaw is active in producing consonantal distinctions, with specific focus on coronal consonants. Therefore, tongue tip and jaw positions are compared for the German coronal consonants /s, f, t, d, n, l/, that is, consonants having the same active articulators (apical/laminal) but differing in manner of articulation. In order to test the stability of articulatory positions for each of these coronal consonants, a natural perturbation paradigm was introduced by recording two levels of vocal effort: comfortable, and loud without shouting. Tongue and jaw movements of five speakers of German were recorded by means of EMMA during /aCa/ sequences. By analyzing the tongue tip and jaw positions and their spatial variability we found that (1) the jaw's contribution to these consonants varies with manner of articulation, and (2) for all coronal consonants the positions are stable across loudness conditions except for those of the nasal. Results are discussed with respect to the tasks of the jaw, and the possible articulatory adjustments that may accompany louder speech.

Interarticulator cohesion within coronal consonant production.

If more than one articulator is involved in the execution of a phonetic task, then the individual articulators have to be temporally coordinated with each other in a lawful manner. The present study aims at analyzing tongue-jaw cohesion in the temporal domain for the German coronal consonants [s, f, t, d, n, l], i.e., consonants produced with the same set of articulators--the tongue blade and the jaw--but differing in manner of articulation. The stability of obtained interaction patterns is evaluated by varying the degree of vocal effort: comfortable and loud. Tongue and jaw movements of five speakers of German were recorded by means of electromagnetic midsagittal articulography (EMMA) during [aCa] sequences. The results indicate that (1) tongue-jaw coordination varies with manner of articulation, i.e., a later onset and offset of the jaw target for the stops compared to the fricatives, the nasal and the lateral; (2) the obtained patterns are stable across vocal effort conditions; (3) the sibilants are produced with smaller standard deviations for latencies and target positions; and (4) adjustments to the lower jaw positions during the surrounding vowels in loud speech occur during the closing and opening movement intervals and not the consonantal target phases.