Voice Onset Time Measurements Research Articles

Voice onset time in bilingual German-Spanish children

This study examines the acquisition of the voicing contrast in German-Spanish bilingual children, on the basis of the acoustic measurement of Voice Onset Time (VOT). VOT in four bilingual children (aged 2;0–3;0) was measured and compared to VOT in three monolingual German children (aged 1;9–2;6), and to previous literature findings in Spanish. All measurements were based on word-initial stops extracted from naturalistic speech recordings. Results revealed that the bilingual children displayed three different patterns of VOT development: 1. Delay in the phonetic realization of voicing: two bilingual children did not acquire long lag stops in German during the testing period; 2. Transfer of voicing features: one child produced German voiced stops with lead voicing and Spanish voiceless stops with long lag voicing; and 3. No cross-language influence in the phonetic realization of voicing. The relevance of the findings for cross-linguistic interaction in bilingual phonetic/phonological development is discussed.

High-speed imaging of the voicing source in laryngectomees during production of voiced-voiceless distinctions for stop consonants

This study presents results from high-speed imaging recordings of the voice source, that is the pharyngo-esophageal segment, in four laryngectomized men. The subjects were asked to produce VCV-syllables with voiced and voiceless stop consonants during simultaneous high-speed imaging recordings and audio recordings. A general and detailed visuo-perceptual analysis of the shape and vibratory pattern in the pharyngo-esophageal (PE-) segment was made, as well as acoustical measurements of voice onset time (VOT) and closure duration for each syllable. The syllables were also audio-perceptually evaluated by five expert listeners. Results show that the subjects had a high overall intelligibility as judged by the listeners. All four subjects were able to make opening gestures in the PE-segment while producing voiceless stop consonants. In cases where misperceptions were predominant, the acoustical analysis with spectrograms and the detailed analysis of the vibration in the PE-segment gave information about probable causes of the mishearings.

An Acoustic Study of Contrasting Plosives and Click Accompaniments in Xhosa

The phonetic manifestation of distinctive plosive types and click accompaniments in Xhosa was investigated with measurements of voice onset time (VOT), closure duration, voicing during closure, and burst amplitude. There is a high degree of interspeaker as well as token-to-token variability in the voiceless unaspirated plosives and clicks concerning their pronunciation with or without audible ejection. The plosives are much more frequently ejective than the corresponding clicks. If present, ejection is manifested by increased VOT, burst amplitude, or both. Duration of voicing during closure is substantial only in the implosive, but not in the ‘voiced’ plosives and clicks. After nasals the percentage of voicing during closure is high in ‘voiced’ plosives due to the very short closure duration found in that context; in the post-nasal ‘voiced’ clicks closure is mostly reduced to zero. Aspirated plosives and clicks in Xhosa show VOT values that are on average relatively long when compared to other languages. Closure duration tends to be shorter in aspirated plosives and clicks than in other categories.

Perception of Voice and Tone Onset Time Continua in Children with Dyslexia with and without Attention Deficit/Hyperactivity Disorder

Tasks assessing perception of a phonemic contrast based on voice onset time (VOT) and a nonspeech analog of a VOT contrast using tone onset time (TOT) were administered to children (ages 7.5 to 15.9 years) identified as having reading disability (RD; n = 21), attention deficit/hyperactivity disorder (ADHD; n = 22), comorbid RD and ADHD (n = 26), or no impairment (NI; n = 26). Children with RD, whether they had been identified as having ADHD or not, exhibited reduced perceptual skills on both tasks as indicated by shallower slopes on category labeling functions and reduced accuracy even at the endpoints of the series where cues are most salient. Correlations between performance on the VOT task and measures of single word decoding and phonemic awareness were significant only in the groups without ADHD. These findings suggest that (a) children with RD have difficulty in processing speech and nonspeech stimuli containing similar auditory temporal cues, (b) phoneme perception is related to phonemic awareness and decoding skills, and (c) the potential presence of ADHD needs to be taken into account in studies of perception in children with RD.

Measurement of Voice Onset Time in Dysarthric Patients: Methodological Considerations

Voice onset time (VOT) reflects the timing control between laryngeal and supralaryngeal adjustments. It has been studied both in normal speakers and patients with speech disorders, but very little information has been published on the feasibility of this measure in clinical practice. We examined 10 repeated utterances involving the voiceless stop consonants [p], [t] and [k] in 110 subjects (27 controls, 48 with spastic dysarthria and 35 with hypokinetic dysarthria). The mean rate of measurable VOT was 95% for normal speech, 80% for hypokinetic dysarthria and 84% for spastic dysarthria. The main obstacle to successful measurement was lack of the burst signifying the release of the plosive. The posterior stop [k] presented the greatest measurement difficulties for the dysarthric subjects, which is in accordance with previous perceptual reports on dysarthria.

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 perceptual characteristics of esophageal and tracheoesophageal speech production

This study comprehensively compared the speech of laryngeal speakers (L), tracheoesophageal speakers (TE), good esophageal speakers (GE), and moderate esophageal speakers (ME) to determine the consequences of TE versus E speech rehabilitation. Twenty speakers (five in each group) were each recorded while reading 16 sentences, and their recordings were analyzed acoustically and perceptually. Acoustic analysis included duration, intensity, fundamental frequency (F0), intonation, and voice onset time measurements. Perceptual analysis included intelligibility and acceptability judgments by naı̈ve listeners. The main acoustic results showed that L speakers differ significantly from all alaryngeal speakers in F0 and intonation production. Moderate esophageal speakers differed significantly from all other groups in duration measures. Perceptual results revealed that L speakers were most intelligible and acceptable, whereas ME speakers were least so. Tracheoesophageal speakers were more acceptable than GE speakers but not more intelligible. Significant correlations emerged between F0, duration measures, and acceptability, and between F0 and intelligibility. Also, a significant correlation emerged between acceptability and intelligibility. Findings emphasized the importance of categorizing esophageal speakers into groups based on their speech proficiency level.

Voice onset time in aphasia, apraxia of speech and dysarthria: a review

Voice onset time (VOT) is an objective temporal acoustic parameter defined as the time between the release of the oral constriction for plosive production and the onset of vocal fold vibrations. Many researchers consider VOT to be the most reliable acoustic cue for the distinction between voiced and voiceless stops. Previous studies have explored the physiological and linguistic factors underlying VOT production in normal speakers across several languages. A major clinical goal of acoustic analysis in speech disorder is to establish a correlation between the acoustic abnormalities and the phonetic perturbations. VOT could thus be used as an acoustic parameter that indicates the phonetic contrast between voiced and voiceless stops. This paper includes a critical review of the measurement of VOT, factors of VOT variability and the effect of neurogenic communication disorders on VOT. We review the VOT data from subjects who exhibit aphasia, apraxia of speech and dysarthria. These studies reveal that VOT perturbations in aphasia have been interpreted as phonemic or phonetic errors, while VOT abnormalities in apraxia of speech and dysarthria grossly reflect loss of motor control.

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 speech produced during simultaneous communication.

This study investigated speaking rate and voice onset time (VOT) in speech produced during simultaneous communication (SC) by speakers with normal hearing. Stimulus words initiated with voiced and voiceless plosives were embedded in a sentence that was spoken and produced with SC. VOT measures were calculated from acoustic recordings and results indicated significant differences between speech-only and SC conditions, with speech produced during SC demonstrating both slower speaking rate and increased VOT of voiceless consonants. VOTs produced during both SC and speech-only conditions followed English voicing rules and varied appropriately with place of articulation. The somewhat enlarged voicing contrast during SC was consistent with previous findings regarding the influence of rate changes on the temporal fine structure of speech (Miller, 1987) and was similar to the voicing contrast results reported for clear speech by Picheny, Durlach, and Braida (1986).

Changes in voice-onset time in speakers with cochlear implants.

Voice-onset time (VOT) and syllable duration were measured for the English plosives in /Cad/(C = consonant) context spoken by four postlingually deafened recipients of multichannel (Ineraid) cochlear implants. Recordings were made of their speech before, and at intervals following, activation of the speech processors of their implants. Three patients reduced mean syllable duration following activation. Using measures of VOT and syllable duration from speakers with normal hearing [Volaitis and Miller, J. Acoust. Soc. Am. 92, 723-735 (1992)] and from the subjects of this study, VOT is shown to vary approximately linearly with syllable duration over the ranges produced here. Therefore, the VOT of each token was adjusted for the change in syllable duration of that token relative to the mean syllable duration in the first baseline session. This variable, labeled VOTc, was used to evaluate the effects on voicing of the speakers' renewed access to the voicing contrast provided by their implants. Preimplant, all four speakers characteristically uttered voiced plosives with too-short VOT, compared to the measures for hearing speakers. Voiceless plosive mean VOT was also abnormally short for two of the speakers, and close to normal for the remaining two. With some hearing restored, subjects made relatively few errors with respect to voicing when identifying plosives in listening tests, and three of the four speakers lengthened VOTc. The findings are interpreted as supporting the hypothesis that speakers use their hearing to calibrate mechanisms of speech production by monitoring the relations between their articulations and their acoustic output.

Voice onset time contrasts in the speech of profoundly hearing impaired children

Children with profound hearing impairments typically err in the production of the voiced voiceless contrast in stops. In order to examine how speech training and experience with various types of prosthetic devices influences these contrasts, four groups of children were recorded producing words beginning with voiced and voiceless stops. Each group was comprised of a conventional hearing aid subject, a tactile aid subject, and a cochlear implant subject. Recordings were made before the children were fitted with either the tactile aid or cochlear implant and 2 years later. Measurements of voice onset time (VOT) were made from the waveforms. Preliminary results from one group of children revealed the voiced and voiceless distinction was correctly produced for bilabial and alveolar stops at both dates. For the velar stops, no child produced a VOT contrast at the first recording date. The child fitted with a cochlear implant produced longer VOTs for voiced velar stops than for voiceless ones. After 2 years experience with the devices, all children demonstrated normal VOT contrasts for velar stops. Data from the remaining three groups will be presented and discussed relative to prosthetic device and experience with the devices. [Work supported by the NIH.]

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.

Acoustic and perceptual analysis of word-initial stop consonants in phonologically disordered children.

Spectrographic measures of voice onset time (VOT) were made for phonologically disordered children in whom a voicing contrast was just beginning to emerge. These temporal measures were related to adult listeners' perception of voicing of the initial stop consonant to determine how well VOT could predict perceived voicing. In general, the predictive utility of VOT was not very high. The relation between VOT as produced by the phonologically disordered children and perceived voicing ranged from 0.31 to 0.43. A finer-grained analysis was conducted to determine what other acoustic cues might have influenced the listeners' judgments of voicing. Although no one acoustic cue could be found to explain all listeners' responses, spectral cues such as fundamental and F1 frequencies at the onset of voicing, as well as the burst and aspiration amplitude relative to the vowel onset amplitude accounted for the perceived voicing of about half of the tokens that were not differentiated by VOT. Rather than relying solely on the temporal characteristics of the VOT interval, a matrix of acoustic cues may influence how a listener perceives word-initial voicing as produced by phonologically disordered children.

The control of voice onset time and vowel duration after paraneoplastic cerebellar degeneration: An acoustic study

Speech production was examined in a group of six subjects with paraneoplastic cerebellar degeneration, a neurological disorder that produces severe dysarthria. Subjects were recorded repeating CVC and CVCV syllables that included the stop consonant [p b t d k g] and the vowels [i a u]. Vowel durations preceding voiced and voiceless segments and voice onset time (VOT) were measured. The vowel duration measures assessed the preservation of intrinsic duration properties, and the variation of these properties in conditioning phonological contexts. The VOT measure assessed the coordination of two independent articulatory events. Results indicated that the cerebellar subjects normally differentiated among individual vowels, and altered vowel duration as a function of phonological context. In contrast, they tended to reduce VOT for voiceless segments, and, in the case of the most impaired subject, the voiceless segments were always perceived as being voiced. Although the VOT durations were reduced, there was no overlap between voiced and voiceless VOTs for most cerebellar subjects. These results suggest that the temporal coordination of articulatory maneuvers rather than general timing of segmental duration may specifically involve the cerebellum. [Work supported by NS 17778.]

Acoustics of stop consonant-vowel relationships during fluent and stuttered utterances

Acoustic duration measures were made on the stop-gap, voice onset time (VOT), and vowel portions of the utterance [tu] in the context “425” as spoken ten times or more by five normal speakers, four mild stutterers, and four severe stutterers. The fluent utterances of the severe stutterers were significantly longer than those of normal speakers on stop-gap and vowel durations but not on voice onset times. Despite the slower speech of the severe stutterers, indications of normalization were found in the relatively stable consonant-to-vowel ratios across groups and in the lack of any significant differences of segment durations as a percentage of total utterance times. Normal speakers and mild stutterers showed an inverse relationship between stop-gap and VOT measures across speakers, but severe stutterers did not maintain this relationship for either fluent or stuttered tokens, nor did a mild stutterer suspected of covert stuttering. Stop-gap durations increased while VOTs stayed within normal limits for fluent tokens. For stuttered tokens, some subjects increased the stop-gap and some the VOT depending upon the location of the block. Abnormal gap to VOT ratios may serve to detect convert stuttering.

The influence of phonetic context on the acoustical properties of stops

In American English, stop consonants may be released, unreleased, or deleted (e.g., the phoneme /t/ in “tea,” “basketball,” and “softly,” respectively). The particular acoustical realization is almost obligatory in some environments and highly variable in others. The purpose of our study was to quantify the influence of context, including syllable structure, on the acoustical properties of stop consonants. Or database consisted of some 5200 stops collected from 1000 sentences. Phonemic transcriptions, including lexical stress and syllable markers, were provided and aligned with the speech waveforms. The stops were grouped into categories corresponding to their position within syllables (e.g., syllable‐initial‐singleton, syllable‐final‐affix, etc.) and marked according to their local phonemic context. Segment durations were measured and the stops were classified as released, unreleased, or deleted on the basis of their duration and voice onset time (VOT). In the analysis of these data, including the examination of VOT and other durational measurements, we found substantial effects of both syllable structure and phonemic context. For example, over 98% of the stops in syllable‐initial position are released, regardless of the preceding phoneme. Syllable‐final singleton stops are released 65% of the time when followed by a vowel (as in “oak is”), and unreleased 73% of the time when followed by a consonant (as in “sickness”). A stop is most likely to be deleted (over 40% of the time) when it is the last member of a syllable‐final cluster containing an obstruent and followed by a syllable‐initial consonant (as in “mostly”). An /s/ preceding a stop consonant or a semivowel following, has a stronger influence on its VOT if it appears within the same syllable. Similarly, a singleton stop's voicing characteristic affects the duration of a preceding vowel differently, depending on whether the two segments are in the same syllable. Detailed results will be presented at the meeting. [Work supported by an AT&T Bell Laboratories Cooperative Research Fellowship and by DARPA.]

Voice onset time in aphasia: Thai II. Production

The aim of this study was to investigate voice onset time (VOT) production in homorganic word-initial stops in Thai in order to explore the nature of speech production deficits across clinical varieties of aphasia. Thai exhibits a three-category distinction in bilabial (/b,p,p h/) and alveolar (/d,t,t, h/) stops, and a two-category distinction in velar (/k,k h/) stops. Subjects included three Broca asphasics, one transcortical motor asphasic, two global asphasics, one conduction aphasic, one Wernicke aphasic, one nonaphasic dysarthric patient, one right-brain-damaged patient, and five normal controls. Test stimuli consisted of eight monosyllabic real words. The results of VOT measurements indicated that Broca and global asphasics exhibited a more severe production disorder than Wernicke, conduction, or transcortical motor asphasics. The right-brain-damaged patient showed no impairment in VOT production. Comparisons are drawn to earlier studies of VOT production in aphasia in two-category languages. Issues concerning the underlying basis of the production deficit for nonfluent aphasics, fluent aphasics, and nonaphasic dysarthrics as well as the relation between perception and production of VOT are discussed.

Speech timing of phonologically disordered children: voicing contrast of initial and final stop consonants.

Speech timing of nine phonologically disordered and nine normally developing children was investigated for the voicing contrasts of word-initial and word-final stop consonants. Measurements of voice onset time, vowel duration, consonant closure duration, and voicing during consonant closure were made from spectrograms. In addition, listener transcriptions were employed for perceptual analysis. Results indicated that some phonologically disordered subjects failed to differentiate VOT in word-initial voiced and voiceless stops, whereas others produced much longer VOTs for voiceless stops than did control subjects. In the word-final voicing contrast, the phonologically disordered children evidenced longer consonant closure durations and less voicing during consonant closure than did normal subjects. However, like normal subjects, they demonstrated differential vowel and consonant closure durations in voiced and voiceless contexts. Perceptual analysis indicated significantly more voicing errors in the initial final stops of phonologically disordered children. These various results are interpreted to mean that some phonologically disordered children may have less mature speech timing control. The implications of these data for the description of voicing errors also are discussed.

VOT im 19. Jahrhundert oder «Die Wiederkehr des Gleichen»

Abstract Up to now the concept of voice onset time (VOT) has been closely associated with the work of Lisker and Abramson. Evidence is presented here that the idea behind it – if not the name – is much older than commonly thought, in fact dating back to the turn of the century. The results of those early VOT measurements are presented and -with respect to Armenian – compared to those arrived at by Lisker and Abramson.