Interarticulator Timing Research Articles

Immediate auditory feedback regulates inter-articulator speech coordination in service to phonetic structure.

Research has shown that talkers reliably coordinate the timing of articulator movements across variation in production rate and syllable stress, and that this precision of inter-articulator timing instantiates phonetic structure in the resulting acoustic signal. We here tested the hypothesis that immediate auditory feedback helps regulate that consistent articulatory timing control. Talkers with normal hearing recorded 480 /tV#Cat/ utterances using electromagnetic articulography, with alternative V (/ɑ/-/ɛ/) and C (/t/-/d/), across variation in production rate (fast-normal) and stress (first syllable stressed-unstressed). Utterances were split between two listening conditions: unmasked and masked. To quantify the effect of immediate auditory feedback on the coordination between the jaw and tongue-tip, the timing of tongue-tip raising onset for C, relative to the jaw opening-closing cycle for V, was obtained in each listening condition. Across both listening conditions, any manipulation that shortened the jaw opening-closing cycle reduced the latency of tongue-tip movement onset, relative to the onset of jaw opening. Moreover, tongue-tip latencies were strongly affiliated with utterance type. During auditory masking, however, tongue-tip latencies were less strongly affiliated with utterance type, demonstrating that talkers use afferent auditory signals in real-time to regulate the precision of inter-articulator timing in service to phonetic structure.

Generalization of inter-articulator timing control: Evidence from tongue-jaw and lip-jaw kinematics using electromagnetic articulography

Recent research in speech production indicates that talkers reliably control the relative timing of articulator movement onsets across variation in production rate, syllable stress, and segmental makeup and that this precision of inter-articulator timing control instantiates phonetic structure. To date, these timing relations have been highly reliable for tongue-jaw kinematics. In the present study, we address the generality of these timing relations to lip-jaw kinematics. Eleven talkers recorded 240 /tV#Cat/ and 240 / bV#Cab/ utterances using electromagnetic articulography, with alternative V (/ɑ/-/ɛ/) and C (/t/−/d/ or /p/−/b/), across changes in production rate (fast-normal) and stress (first syllable stressed-unstressed). To quantify inter-articulator temporal coordination, the timing of either tongue-tip or lower-lip raising onset for the intervocalic C, relative to the jaw opening-closing cycle for V, was obtained. Results indicate that the same kinematic pattern occurred among both sets of articulators: any manipulation that shortened the jaw opening-closing cycle reduced the latency of either tongue-tip or lower-lip movement onset, relative to the onset of jaw opening. Furthermore, the movement onset latencies of the tongue-tip and lower-lip were both highly differentiated by utterance type, bolstering the view that inter-articulator timing relations instantiate phonetic structure in the resulting acoustic signal.

The effect of increased vocal intensity on interarticulator timing in speakers with Parkinson's disease: A preliminary analysis

PurposeThe purpose of the current study was to investigate the effect of increased vocal intensity on interarticulator timing in individuals with Parkinson's disease (PD). MethodsTen individuals with mild to moderate hypophonia, secondary to PD, were selected for study. Over an 8-week treatment period, multi-talker babble noise was presented monaurally to the individuals with PD during everyday communication contexts to elicit increased vocal intensity (Lombard effect). Outcome measures included sound pressure level (SPL), voice onset time (VOT), VOT ratio, percent voicing, and speech intelligibility. ResultsGroup and individual participant responses to the treatment are reported and discussed. Speakers with PD were shown to significantly increase SPL in response to treatment. Six of the 10 speakers showed improved temporal coordination between the laryngeal and supralaryngeal mechanisms (interarticulator timing) in response to treatment. Four of the 10 speakers, however, showed reduced laryngeal–supralaryngeal timing at the end of treatment. Group speech intelligibility scores were significantly higher post-treatment as compared to pre-treatment. ConclusionsVoice treatment during everyday communication resulted in improved temporal coordination across the laryngeal and supralaryngeal mechanisms for the majority of speakers with PD and made them easier to understand. Further investigations are planned to explore individual differences in response to treatment. The identification of speaker-specific voicing and devoicing strategies is consistent with the heterogeneous nature of PD.Learning outcomes: Readers will be able to: 1. Describe the speech and voice characteristics of individuals with Parkinson's disease. 2. Define the Lombard effect. 3. Describe acoustic measures of voice onset time and percent voicing. 4. Describe the effect of voice treatment on voice onset time and percent voicing in individuals with Parkinson's disease.

Interarticulator Timing Control During Inspiratory Phonation

The ability of Cantonese speakers in producing aspirated and unaspirated stops and stops at different places of articulation using expiratory phonation (EP) and inspiratory phonation (IP) was compared. Interarticulator timing during stop production using EP and IP was examined. Voice onset time (VOT) associated with EP and IP stops was compared with stop identification scores by naïve listeners. Aspirated and unaspirated voiceless stops (/p(h), t(h), k(h), p, t, k/) followed by the vowel /a/ were produced by 15 male and 15 female Cantonese speakers using EP and IP. VOT values were measured and isolated speech samples of stop productions were identified by 10 naïve listeners. Percent correct identification of stops was obtained from the 10 listeners. Perceptual data showed that production of IP stops were associated with reduced accuracy in stop identification, with predominant errors in aspiration perception. Acoustic analysis showed that IP stops were generally produced with significantly shorter VOT than their EP counterparts. In addition, effect of place of articulation on VOT was also found for both IP and EP stops, notably with velar stops being associated with significantly longer VOT values than bilabial and alveolar stops. The findings that IP stops were produced with shorter VOT as compared with EP stops imply that the articulatory-phonatory coordination during IP was not the same as that during EP, causing a discrepancy in the timing control between articulators.

Interarticulator timing in a sentence production in young normal speakers and speakers with apraxia of speech.

Apraxia of speech (AOS) is typically considered as characterized by kinematic timing problems among articulators; however, kinematic descriptions of such phenomenon are scarce. The goal of this study was to describe articulatory timing between the lips and jaw and the lips and tongue in young normal and AOS speakers across three speaking rates, using x‐ray microbeam data. Data of young normal speakers were taken from the x‐ray microbeam speech production database. Lip protrusion and tongue elevation timings were derived from the kinematic and acoustic data in the production of “too” in the sentence “The other one is too big” and lip and jaw closing timings for /b/ and /w/ were derived from the kinematic data of the same sentence. The temporal relationships between these articulatory movements in each event were then examined with consideration of the effect of speaking rate. The results are discussed in relation to the effect of speaking rate on interarticulator timing and interspeaker variability in interarticulator timing.

Effect of tone on voice onset time in laryngeal and esophageal speech of Mandarin

Defined as the time between the release of burst of a stop and the onset of the following vowel, voice onset time (VOT) directly indicates the interarticulator timing between the voicing source and the articulatory movement in the vocal tract. A number of studies have investigated the VOT characteristics of different languages. Yet, few have studied how VOT is affected by tone level in a tone language, and by the type of phonation. The present study investigated the possible effect of tone level and phonation type on such interarticulator timing characteristics. VOT values were measured from the syllables /pha/, /tha/, and /kha/ produced at four Mandarin tone levels by eight laryngeal (NL) and seven esophageal (SE) speakers who were native speakers of Mandarin. Results indicated that significant differences in VOT were found in the NL speaker group, but not in the SE speaker group. With respect to phonation type, SE speakers showed significantly shorter VOT values than NL speakers. Such differences may be related to the use of pharyngoesophageal (PE) segment as a new sound source. SE speakers appear to take a shorter time to start PE segment vibration as compared to NL speakers.

Producing VOT contrasts

The development of voice onset time (VOT) as an acoustic index for studying and classifying stop consonants also prompted a large number of studies examining laryngeal activity and interarticulator timing related to VOT. A collaboration between the Research Institute of Logopedics and Phoniatrics at the University of Tokyo and Haskins Laboratories resulted in a long line of studies using electromyographic and other techniques that provided much of the empirical foundations for what we know about laryngeal function in speech, in particular the production of voiced and voiceless consonants. This presentation will review the articulatory control of VOT differences. To make a consonant voiceless, a speaker uses a combination of glottal abduction and vocal fold tensing. The distinction between voiceless stops with long and short VOT is basically due to a difference in the timing between the glottal abduction gesture and the oral closing and opening gestures. Variations in the size of the glottal gesture also occur. More generally, variations in interarticulator timing between glottal and oral movements are used to produce the different stop categories that occur in the languages of the world. [Work supported by NIH.]

An approach to real-time magnetic resonance imaging for speech production.

Magnetic resonance imaging (MRI) has served as a valuable tool for studying static postures in speech production. Now, recent improvements in temporal resolution are making it possible to examine the dynamics of vocal-tract shaping during fluent speech using MRI. The present study uses spiral k-space acquisitions with a low flip-angle gradient echo pulse sequence on a conventional GE Signa 1.5-T CV/i scanner. This strategy allows for acquisition rates of 8-9 images per second and reconstruction rates of 20-24 images per second, making veridical movies of speech production now possible. Segmental durations, positions, and interarticulator timing can all be quantitatively evaluated. Data show clear real-time movements of the lips, tongue, and velum. Sample movies and data analysis strategies are presented.

An approach to real-time magnetic resonance imaging for speech production

Magnetic resonance imaging has served as a valuable tool for studying primarily static postures in speech production. Now, recent improvements in imaging techniques, particularly in temporal resolution, are making it possible to examine the dynamics of vocal tract shaping during speech. Examples include Mady et al. (2001, 2002) (8 images/second, T1 fast gradient echo) and Demolin et al. (2000) (4–5 images/second, ultra fast turbo spin echo sequence). The present study uses a non 2D-FFT acquisition strategy (spiral k-space trajectory) on a GE Signa 1.5T CV/i scanner with a low-flip angle spiral gradient echo originally developed for cardiac imaging [Kerr et al. (1997), Nayak et al. (2001)] with reconstruction rates of 8–10 images/second. The experimental stimuli included English sentences varying the syllable position of /n, r, l/ (spoken by 2 subjects) and Tamil sentences varying among five liquids (spoken by one subject). The imaging parameters were the following: 15 deg flip angle, 20-interleaves, 6.7 ms TR, 1.88 mm resolution over a 20 cm FOV, 5 mm slice thickness, and 2.4 ms spiral readouts. Data show clear real-time movements of the lips, tongue and velum. Sample movies and data analysis strategies will be presented. Segmental durations, positions, and inter-articulator timing can all be quantitatively evaluated. [Work supported by NIH.]

Articulatory control of vowel length for contiguous jaw cycles: the effects of speaking rate and phonetic context.

The current study examined contiguous cycles of jaw movement in order to determine if select suprasegmental manipulations operate globally across the entire utterance, while phonetic changes are more locally administered. Specifically, articulatory kinematics were examined to determine if intra- and inter-articulatory spatial and temporal organization across manipulations of speaking rate was maintained for both jaw cycles while differing between the two cycles for phonetic changes (i.e., in coda composition) specific to the second jaw cycle. Five normal speakers repeated the syllables /paep/, /paeps/, and /paepst/, embedded in the carrier phrase, "Now say again," using slow, normal, and fast speaking rates. Measures were made of the magnitude of jaw opening peak velocity and time to peak velocity, as well as of coarticulatory overlap and interarticulator timing, for the first jaw cycle (jaw lowering for /eI/ in "say" to the first /p/) and the second jaw cycle (jaw lowering for /ae/ to the second /p/). The current data indicate that, for intra-articulatory kinematics, the manipulation of phonetic context resulted in localized adjustments, whereas the manipulation of speaking rate was applied globally across the utterance. Conversely, for inter-articulatory kinematics, the upper lip-jaw synergy was reconfigured across the utterance for manipulations of speaking rate, whereas this synergy was maintained for localized manipulations in phonetic context. Results are discussed with respect to motor strategies being flexibly implemented as a result of contextual variation and speech rate.

Relative timing of the three gestures of North American English /r/

Interarticulator timing of liquid consonants has been shown in recent years to be of importance in understanding syllable-based allophonic variation and related synchronic, historical, and developmental phonological phenomena. In this and other respects, the unusual complexity of North American English /r/ in particular has attracted much attention. Nevertheless, because of the difficulty of collecting simultaneous dynamic measurements of the lips, tongue body and tongue root, the articulatory dynamics of /r/ remain a subject of conjecture. A simultaneous ultrasound and video study of relative timing of these three gestures of /r/ will be presented. Preliminary results from three native North American English speakers show that, for the prevocalic allophone, the lip gesture reaches its target first, followed by the tongue body (TB) gesture, then the tongue root (TR) gesture last. As for the postvocalic allophone, the lip and TR constrictions are reduced in magnitude; also the TR gesture tends to precede the other gestures in both gestural onset and peak. These results support a view of the lip gesture of /r/ as a consonantal component, and presents a pattern for /r/ analogous to that previously observed for /l/. [Research supported by NSERC and NIH.]

Laryngeal factors in voiceless consonant production in men, women, and 5-year-olds.

Voicing control in stop consonants has often been measured by means of voice onset time (VOT) and discussed in terms of interarticulator timing. However, control of voicing also involves details of laryngeal setting and management of sub- and supraglottal pressure levels, and many of these factors are known to undergo developmental change. Mechanical and aerodynamic conditions at the glottis may therefore vary considerably in normal populations as functions of age and/or sex. The current study collected oral airflow, intraoral pressure, and acoustic signals from normal English-speaking adults and children producing stop consonants and /h/ embedded in a short carrier utterance. Measures were made of stop VOTs, /h/ voicing and flow characteristics, and subglottal pressure during /p/ closures. Clear age and gender effects were observed for /h/: Fully voiced /h/ was most common in men, and /h/ voicing and flow data showed the highest variability among the 5-year-olds. For individual participants, distributional measures of VOT in /p t/ were correlated with distributional measures of voicing in /h/. The data indicate that one cannot assume comparable laryngeal conditions across speaker groups. This, in turn, implies that VOT acquisition in children cannot be interpreted purely in terms of developing interarticulator timing control, but must also reflect growing mastery over voicing itself. Further, differences in laryngeal structure and aerodynamic quantities may require men and women to adopt somewhat different strategies for achieving distinctive consonantal voicing contrasts.

Acoustic and articulatory differences across word position for American English /r/

Typically, American English /r/ is manifested with different formant frequency patterns in word-initial, word-final and word-medial position. In particular, it has been reported (Lehiste, 1962; Espy-Wilson, 1992) that initial /r/’s show lower third formants. This may be due to differences in position or configuration of the primary articulator for /r/—the tongue—or it may reflect an increased degree of lip-rounding. Differences in tongue shape across word position have been reported (Zawadaski and Kuehn, 1982), but it is not clear how reported differences may relate to formant lowering. In this study, eight native speakers of American English recorded words with initial, final and medial /r/’s. Articulatory movements of the tongue tip, tongue blade and tongue dorsum, lips and jaw were tracked simultaneously by Electro-Magnetic Midsagittal Articulometer (EMMA). For each speaker, we compare spatial position, time course, and trajectory for articulators across positional variants. Preliminary data suggest that tongue articulators show similar time course in all three positions. Results are discussed with regard to acoustical modeling studies, theories of articulatory strengthening and interarticulator timing. [Research supported by NIH and NSF.]

Kinematics of compensatory vowel shortening: Intra and interarticulatory timing

The acoustic shortening of vowels has been demonstrated to occur across a variety of contextual variations. The current study examined the kinematic adjustments involved in vowel shortening, as a function of speaking rate and coda composition (singleton consonants versus consonant clusters). Five normal speakers repeated the syllables /paep/, /paeps/, and /paepst/, embedded in a carrier phrase, across three distinct speaking rates (slow, normal, and fast). Changes in the timing of the jaw-closing gesture for post-vocalic bilabial production, and in the upper lip–jaw timing relationship (measured via phase angles), were examined. The onset of the jaw-closing gesture typically shifted earlier in the cycle of jaw movement for consonant cluster productions, across all speaking rates. Subject-specific modifications of interarticulator timing were observed, with some speakers adjusting upper lip movement in order to maintain constant timing with the jaw, while others tended to dissociate the upper lip and jaw. Both coda composition and speaking-rate manipulations resulted in substantial intersubject variability in the lip–jaw timing relationship. These findings suggest that, in order to achieve the intended acoustic-perceptual goals, articulatory coordination may not be absolutely invariant, but rather, systematically and individually organized across task manipulations. [Work supported by CRDF-University of Pittsburgh and NSERC.]

Interarticulator programming in VCV sequences: lip and tongue movements.

This study examined the temporal phasing of tongue and lip movements in vowel-consonant-vowel sequences where the consonant is a bilabial stop consonant /p, b/ and the vowels one of /i, a, u/; only asymmetrical vowel contexts were included in the analysis. Four subjects participated. Articulatory movements were recorded using a magnetometer system. The onset of the tongue movement from the first to the second vowel almost always occurred before the oral closure. Most of the tongue movement trajectory from the first to the second vowel took place during the oral closure for the stop. For all subjects, the onset of the tongue movement occurred earlier with respect to the onset of the lip closing movement as the tongue movement trajectory increased. The influence of consonant voicing and vowel context on interarticulator timing and tongue movement kinematics varied across subjects. Overall, the results are compatible with the hypothesis that there is a temporal window before the oral closure for the stop during which the tongue movement can start. A very early onset of the tongue movement relative to the stop closure together with an extensive movement before the closure would most likely produce an extra vowel sound before the closure.

Intrinsic and extrinsic timing in stutterers' speech: data and implications.

This study examined interarticulator timing amongst stutterers and non-stutterers from the perspective of extrinsic and intrinsic timing models of speech motor control. Timing relationships were examined for an oral closure task across stress, rate, and vowel differences. Sequential aspects of extrinsic timing theories were analyzed by peak velocity sequence profiles of upper lip, lower lip, and jaw, and nonsequential aspects by sequence period (the time period covering all three of the articulator peak velocity onsets times irrespective of sequencing order). Intrinsic timing theory was modeled using phase portrait analyses of the same data. Consistently greater phase angle variability was seen amongst the stutterers, and variability was found to be significantly greater at a faster articulatory rate and when altered stress patterns were required. No group differences were found for peak velocity sequencing, but the (sequence independent) sequence period data somewhat mirrored the phase angle findings. This finding calls into question the notion that phase angle analyses reflect purely intrinsic timing phenomena.

The vowel lengthening exaggeration effect in speakers with apraxia of speech: Compensation, artifact, or primary deficit?

Vowel duration functions contrastively in English to signal the voicing feature of syllable-final stop consonants. This study examines three hypotheses posited to explain why speakers with apraxia of speech and a concomitant aphasia exhibit an exaggerated vowel lengthening effect relative to speakers with dysarthria, aphasia without apraxia and controls. The investigation addresses the hypotheses that the vowel lengthening exaggeration effect is attributable to: (1) a compensatory strategy, (2) an artifact of slow speaking rate, (3) the concomitant language impairment, or (4) a primary deficit reflecting the underlying nature of the apraxia disorder. The results do not support the first three of these hypotheses. It is hypothesized that the temporal measures most likely to reveal abnormalities which are uniquely characteristic of speakers with apraxia of speech are those which are relational in nature, either with respect to inter-articulator timing or contrastive durations.

Acoustic and aerodynamic effects of interarticulator timing in voiceless consonants.

Interarticulator timing is a mechanism for producing linguistic contrasts that is widely used in different languages. This paper explores acoustic and aerodynamic effects of variations in laryngeal-oral coordination in voiceless consonants. Measurements of voice onset time and interarticulator phasing for individual tokens of stop consonants show weak correlations, indicating that interarticulator timing is only one factor determining voice onset time. Other factors most likely involved are glottal opening, transglottal pressure and air flow, and vocal fold tension. Taken together, these observations suggest that speakers may only have limited control of voice onset time. This could explain why languages do not seem to make fine-grain use of VOT for linguistic contrasts. Measurements of peak and minimum air flow during individual source pulses, obtained by inverse-filtering oral flow, show a pattern of decrease and increase in vowels following voiceless consonants. Subtle differences in the time course of these patterns occur following different consonants, suggesting that interarticulator phasing may be partly responsible for them. Closer examination reveals consistent correlations with interarticulator phasing for one speaker but inconsistent results for another. The results are discussed in terms of speech motor control and controlled variables in speech.

Anticipatory and carry-over nasal coarticulation in the speech of children and adults.

Producing (n) requires a lingual constriction to be formed and the velopharyngeal port (VPP) to be opened. This study examined interarticulator timing in the speech of adults and children aged 5 and 10 years. A new acoustic method was developed to determine the time at which VPP opening began during vowels spoken in the context of (d-n), and VPP closing reached completion in vowels spoken in the context of (n-d). Adults and children alike nasalized most of the vowels in the (d-n) context. This suggested that the children's speech was not more "segmental" than adults'. It suggested, further, that nasalizing vowels in a (d-n) context is a natural speech process that need not be learned by young children. The children, like the adults, nasalized most of the vowels spoken in the context of (n-d). The lack of significant between-group differences, taken together with several other findings of the study, is consistent with the view that the temporal domain of carry-over nasal coarticulation is determined largely by the time needed to close the VPP (i.e., by inertial properties of the speech production mechanism).

Laryngeal kinematics in voiceless obstruents produced by hearing-impaired speakers.

During normal production of voiceless consonants several events occur simultaneously in the vocal tract. These events must be temporally coordinated. Earlier work has indicated that a breakdown in interarticulator timing can contribute to the characteristic voiced-voiceless errors produced by hearing-impaired speakers. The present study examines kinematic details of the laryngeal articulatory gesture in 2 deaf speakers and a control subject using transillumination of the larynx. Results indicate that hearing-impaired speakers often do not produce differences between stops and fricatives in the kinematic details of the gesture. That is to say, although hearing speakers commonly use a larger laryngeal gesture for fricatives than for stops and also show durational differences of the abduction and the adduction phases between phonetic categories, the hearing-impaired subjects did not make them. Also, the deaf speakers participating in this study were more variable in the kinematic measures.