Avraham Parush

Characteristics of Velocity Profiles of Speech Movements

The control of individual speech gestures was investigated by examining laryngeal and tongue movements during vowel and consonant production. A number of linguistic manipulations known to alter the durational characteristics of speech (i.e., speech rate, lexical stress, and phonemic identity) were tested. In all cases a consistent pattern was observed in the kinematics of the laryngeal and tongue gestures. The ratio of maximum instantaneous velocity to movement amplitude, a kinematic index of mass-normalized stiffness, was found to increase systematically as movement duration decreased. Specifically, the ratio of maximum velocity to movement amplitude varied as a function of a parameter, C, times the reciprocal of movement duration. The conformity of the data to this relation indicates that durational change is accomplished by scalar adjustment of a base velocity form. These findings are consistent with the idea that kinematic change is produced by the specification of articulator stiffness.

Similarities in the Control of the Speech Articulators and the Limbs: Kinematics of Tongue Dorsum Movement in Speech

The kinematics of tongue dorsum movements in speech were studied with pulsed ultrasound to assess similarities in the voluntary control of the speech articulators and the limbs. The stimuli were consonant--vowel syllables in which speech rate and stress were varied. The kinematic patterns for tongue dorsum movements were comparable to those observed in the rapid movement of the arms and hands. The maximum velocity of tongue dorsum raising and lowering was correlated with the extent of the gesture. The slope of the relationship differed for stressed and unstressed vowels but was unaffected by differences in speech rate. At each stress level the correlation between displacement and peak velocity was accompanied by a relatively constant interval from the initiation of the movement to the point of maximum velocity. The data are discussed with reference to systems that can be described with second-order differential equations. The increase in the slope of the displacement/peak-velocity relationship for unstressed versus stressed vowels is suggestive of a tonic increase in articulator stiffness. Variations in displacement are attributed to the level of phasic activity in the muscles producing the gesture.

A kinematic study of lingual coarticulation in VCV sequences

Intra-articulator anticipatory and carryover coarticulation were assessed in both temporal and spatial terms. Three subjects produced VCV sequences with velar stop consonants and back vowels. Pulsed ultrasound was used to examine the vertical displacement, duration, and maximum velocity of the tongue dorsum raising (VC transition) and lowering (CV transition) gestures. Anticipatory coarticulation was primarily temporal for two subjects, with decreases in the duration of the VC transition accompanying increases in displacement for the CV transition. Carryover coarticulation was primarily spatial for all three subjects, with decreases in CV displacement and maximum velocity accompanying increases in VC displacement. It is suggested that these intra-articulator patterns can be accounted for in terms of an interaction between the raising gesture and a vowel-specific onset time of the lowering gesture towards the vowel. The implications of this kinematic characterization are discussed.

Superior lateral pharyngeal wall movements in speech

Medial movements of the lateral pharyngeal wall at the level of the velopharyngeal port were examined by using a computerized ultrasound system. Subjects produced CVNVC sequences involving all combinations of the vowels /a/ and /u/ and the nasal consonants /n/ and /m/. The effects of both vowels on the CVN and NVC gestures (opening and closing of the velopharyngeal port, respectively) were assessed in terms of movement amplitude, duration, and movement onset time. The amplitude of both opening and closing gestures of the lateral pharyngeal wall was less in the context of the vowel /u/ than the vowel /a/. In addition, the onset of the opening gesture towards the nasal consonant was related to the identity of both the initial and the final vowels. The characteristics of the functional coupling of the velum and lateral pharyngeal wall in speech are discussed.

Lower pharyngeal wall coarticulation in VCV syllables

Speech movements of the lower pharyngeal wall were recorded in two subjects using pulsed-echo ultrasound. The focus of the study was the pattern of coarticulation of pharyngeal wall movements. Using nonsense utterances as test material, both anticipatory and carryover coarticulatory effects were observed. The identity of the final vowel in VCV sequences affected the kinematic characteristics of the initial VC transition. Both the amplitude and the duration of the movement between the initial vowel and the consonant were greater when the final vowel was /u/ rather than /a/. Similarly, the initial vowel affected the kinematic characteristics of the final CV transition. The amplitude of the movement from the consonant to the final vowel was greater with the initial vowel /u/ as opposed to /a/. The coarticulatory patterns observed in this study are similar to those previously reported for the tongue dorsum and upper pharynx [Parush et al., J. Acoust. Soc. Am. 74, 1115-1125 (1983); Parush and Ostry, J. Acoust. Soc. Am. 80, 749-756 (1986)].

Computerized pulsed‐ultrasound techniques for the measurement of lingual, laryngeal, and lateral pharyngeal wall movements

Keller and Ostry (J. Acoust. Soc. Am., in press) described a microcomputer‐based system for the measurement of tongue dorsum movements with pulsed‐echo ultrasound. We have recently completed an upgrade of this system to provide facilities for (1) simultaneous ultrasound measurement of any two of lingual, larygeal, and lateral pharyngeal wall movements, (2) the transduction of jaw movements and force. (3) concurrent EMG sampling, and (4) acoustic sampling at rates up to 7 kHz. The presentation focuses on the pulsed‐ultrasound recording, display, and analysis techniques. The transducer placement procedures for tongue dorsum, vocal folds, and lateral pharyngeal wall are described and several examples of simultaneous recordings are presented. Data analysis techniques involving separate application of natural cubic spline functions to each of the records are also presented and an iterative procedure for optimizing goodness of fit of the spline functions is described.

Coarticulation in lateral pharyngeal wall movements

Medial movements of the lateral pharyngeal wall (LPW) at the level of the velopharyngeal port were examined using a computerized ultrasound system. Subjects produced CVNVC sequences with all combinations of the vowels /a/ and /u/, and the nasal consonants /n/ and /m/. The flanking consonants were always /p/. The effects of either vowel upon the CVN or NVC gestures (opening or closing of the velopharyngeal port, respectively) were assessed in terms of displacement, duration, and movement onset time. Both CVN and NVC gestures were primarily affected by the initial vowel: movements had less displacement when the initial vowel was /a/. The onset of the CVN (opening) gesture was affected by the final vowel: the movement started earlier, during initial consonant closure, when the final vowel was /a/. In addition, the duration of this gesture was longer when the final vowel was /a/. Finally, no consistent carryover effects of the initial vowel were found upon the onset time or duration of the NVC gesture. The fi...

Control of rate and movement duration in speech

This paper provides evidence on the control of rate and movement duration in speech. A computerized pulsed‐ultrasound system was used to monitor separately tongue dorsum movements and laryngeal gestures during the production of CV and CVCVC sequences. The kinematics of tongue and laryngeal movements were analysed by partitioning the lowering gesture of the tongue and both the abduction and addution gestures of the vocal folds to give estimates of displacement, duration, and maximum velocity. For both articulators the ratio of the maximum velocity to the extent of the gesture was found to vary inversely with the duration of the movement. The finding suggests that a single function might account for a wide range of changes in the duration of individual gestures. The control of movement rate and duration through the regulation of biomechanical characteristics of speech articulators is discussed.

Lingual velocity and onset of voicing

The timing of tongue movements was studied in relation to oral release and onset of voicing, using pulsed‐echo ultrasound. The stimuli were CV syllables, produced at two speech rates and different stress patterns. Relationships between the timing of maximum velocity on tongue lowering, oral release, and voice onset were examined. The interval from oral release to the point of maximum lowering velocity was essentially constant across differences in speech rate, voicing, and vowel height, though estimates differed for stressed and unstressed vowels. For unstressed vowels, peak lowering velocity lagged oral release by approximately 5 ms; for stressed vowels the delay was about 35 ms. The interval from the point of maximum velocity to voice onset was highly correlated with VOT. Further, for stressed vowels, VOT was inversely related to the maximum velocity of tongue lowering and to the distance to the point of maximum velocity from linguo‐palatal contact. As reported by others, VOT varied with speech rate, co...

Lingual coarticulation in VCV sequences

Pulsed‐echo ultrasound was used to study coarticulation in tongue dorsum movements during the production of VCV sequences. The stimuli were velar stop consonants /k/ and /g/ combined with posterior vowels /a/, /o/, and /u/. Vertical displacement, maximum velocity, and duration were obtained for all V1C and CV2 transitions. Right‐left (effect of CV2 on V1C) and left‐right (effect of V1C on CV2) coarticulation Was examined by stepwise multiple regression. Highly significant effects were obtained with /a/. Total duration of V1C was negatively related both to displacement from linguo‐palatal contact to the point of maximum velocity and to total displacement of CV2 (RL effects). Total displacement and maximum velocity of CV2 were negatively related to the displacement to the point of maximum velocity and total displacement of V1C (LR effects). The LR effects of V1C on CV2 were larger than the corresponding RL effects. Similar patterns were obtained for both intervocalic consonants. The findings are discussed in terms of the contributions of mechano‐inertial and motor timing effects to coarticulation.