Voice Onset Time Differences Research Articles

Variation in Voice Onset Time of Stops: The Case of Chinese Korean

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Phonemic contrast enhancement in clear speech production: The case of Korean stop production

This study explores the code enhancement aspect of clear speech production. Younger (n=11, 20–29 years old) and older (n=11, 40–60 years old) speakers of Korean produced the three series of Korean stops (aspirated, lenis, fortis) in three different speaking styles: conversational, citation-form, and clear speech. The production of Korean stops was analyzed for three acoustic properties differentiating the Korean stops, voice onset time (VOT), amplitude difference between the first and the second harmonics (H1-H2), and fundamental frequency (F0). For both of the younger and older groups, the VOT difference between the aspirated and lenis stops was enhanced in clear speech, in addition to enhanced difference between the aspirated/lenis and fortis stops for H1-H2. The two groups differed in that only the younger speakers showed a substantial increase in F0 for the production of the aspirated stops in clear speech. Also, there was a substantial degree of interspeaker variability in the size and direction of the acoustic adjustment in clear speech. The results of this study support Silva’s [Phonology 23, 287–308 (2006)] proposal that younger and older Korean speakers may use different strategies in order to maintain a distinction between the three types of Korean stops.

The relation between focus effects in production and exemplar locations in perception for stop types in English, Japanese, and Korean

This paper examines focus‐induced variability in the production of labial stop contrasts in English, Japanese, and Korean, pursuing differences between the languages in how voice onset time (VOT) and fundamental frequency (F0) are used to indicate differences between stop types. Language differences are compared to differences in the perceptual usage of these acoustic cues using AMBEL, an adaptive tracking algorithm that allows subjects to search multi‐dimensional stimulus arrays for best exemplars. All three languages exhibit category differences in VOT, though Japanese and Korean exhibit overlap for two of the categories. As found previously, for these categories, both Japanese and Korean exhibit large differences in F0 in the following vowel. Except for the smaller F0 differences in English, all of these VOT and F0 differences are systematically expanded in a focus condition. In particular, VOT increases for the more aspirated stops in all three languages, and substantial rising F0 patterns are observed in lenis Korean and zero‐lag Japanese stops. Perceptual data match these focus effects; best exemplars differ in VOT in all three languages, and in Japanese and Korean, where substantial F0 focus effects were observed, F0 differences affect the identification of best exemplars. [Work supported by NSF.]

An acoustic and perceptual study of initial stops produced by profoundly hearing impaired adolescents

This study investigated the role of Voice Onset Time (VOT) as perceptual cue to the aspiration contrast of Cantonese initial stops produced by adolescent profoundly hearing impaired speakers. Speakers with normal hearing signalled the aspiration contrast through VOT differences. Hearing impaired speakers produced initial stops with no significant VOT differences between aspirated and unaspirated stops; the accuracy of perception were above chance level for unaspirated stops but were below chance level for aspirated stops. Discriminant analysis conducted on data from a perceptual task showed that listeners with normal hearing relied on VOT cue for aspiration contrast of initial stops produced by control speakers. By contrast, stops produced by the hearing impaired speakers were not distinguished by listeners on the basis of VOT in that listeners were able to rely on VOT as a perceptual cue only to unaspirated stops, but not to aspirated stops.

Effect of speaking rate on individual talker differences in voice-onset-time

Recent findings indicate that individual talkers systematically differ in phonetically relevant properties of speech. One such property is voice-onset-time (VOT) in word-initial voiceless stop consonants: at a given rate of speech, some talkers have longer VOTs than others. It is also known that for any given talker, VOT increases as speaking rate slows. We examined whether the pattern of individual differences in VOT holds across variation in rate. For example, if a given talker has relatively short VOTs at one rate, does that talker also have relatively short VOTs at a different rate? Numerous tokens of /ti/ were elicited from ten talkers across a range of rates using a magnitude-production procedure. VOT and syllable duration (a metric of speaking rate) were measured for each token. As expected, VOT increased as syllable duration increased (i.e., rate slowed) for each talker. However, the slopes as well as the intercepts of the functions relating VOT to syllable duration differed significantly across talkers. As a consequence, a talker with relatively short VOTs at one rate could have relatively long VOTs at another rate. Thus the pattern of individual talker differences in VOT is rate dependent. [Work supported by NIH/NIDCD.]

The interaction between metrical structure and tone in Kera

This paper examines the cues for and interaction between the metrical and tonal systems of Kera. Kera has no word-level stress, but the heads of its quantity-sensitive iambic feet are cued by duration, intensity and vowel allophony; in addition, foot boundaries are identified by vowel-harmony and tone-spreading domains. The tonal system has three underlying tones, which are enhanced by differences in voice onset time (VOT). Kera demonstrates an interaction between the iambic foot and tone. Words have one or two tones. For words of three or more syllables the tone-bearing unit is the foot, but for shorter words it is the syllable. This dichotomy is accounted for by a faithfulness constraint requiring all tones to surface, which overrides a constraint limiting each foot to one tone. Kera shows that a tonal system can be sensitive to metrical structure, while maintaining a certain independence between the two systems.

Acoustic evidence for the emergence of tonal contrast in contemporary Korean

Acoustic evidence suggests that contemporary Seoul Korean may be developing a tonal system, which is arising in the context of a nearly completed change in how speakers use voice onset time (VOT) to mark the language’s distinction among tense, lax and aspirated stops. Data from 36 native speakers of varying ages indicate that while VOT for tense stops has not changed since the 1960s, VOT differences between lax and aspirated stops have decreased, in some cases to the point of complete overlap. Concurrently, the mean F0 for words beginning with lax stops is significantly lower than the mean F0 for comparable words beginning with tense or aspirated stops. Hence the underlying contrast between lax and aspirated stops is maintained by younger speakers, but is phonetically manifested in terms of differentiated tonal melodies : laryngeally unmarked (lax) stops trigger the introduction of a default L tone, while laryngeally marked stops (aspirated and tense) introduce H, triggered by a feature specification for [stiff ].

Training to use voice onset time as a cue to talker identification induces a left-ear/right-hemisphere processing advantage

We examined the effect of perceptual training on a well-established hemispheric asymmetry in speech processing. Eighteen listeners were trained to use a within-category difference in voice onset time (VOT) to cue talker identity. Successful learners ( n = 8) showed faster response times for stimuli presented only to the left ear than for those presented only to the right. The development of a left-ear/right-hemisphere advantage for processing a prototypically phonetic cue supports a model of speech perception in which lateralization is driven by functional demands (talker identification vs. phonetic categorization) rather than by acoustic stimulus properties alone.

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.

Acoustics of clear speech from children with normal hearing and cochlear implants

It is common among clinicians to ask children to produce their best speech during intervention. However, it is unclear whether children know how to respond to these directions and whether any contingent changes in their production actually result in better speech. Normal and best speech for children with normal hearing (NH) and cochlear implants (CI) were compared on a variety of acoustic measures. The children (7 to 14 years of age) were asked to read ten simple sentences to train up a fictional automatic speech recognizer for children. They subsequently produced the same sentences with their best and then very best, very clearest speech (ostensibly to test the recognizer). Sentence, pause, and vowel duration were calculated for all sentences as well as vowel intensity and fundamental frequency. Additionally, phonetic distinctiveness was evaluated through vowel space size and voice onset time differences between voiced and voiceless stops. NH children demonstrated patterns of best speech that resemble adult clear speech productions. CI children’s speech resembled NH best speech in all elicitation conditions, except that they slowed (their already slower) speaking rate for best speech. The results indicate that clear speech can be produced by children. [Work supported by NIH.]

Variation in Voice Onset Time for Korean Stops

Abstract. Acoustic data elicited from 34 native speakers of Korean living in the United States pro-vide evidence for diachronic change in the voice onset time (VOT) of phrase-initial aspirated and lax stop phonemes. While older speakers produce aspirated and lax stops with clearly differentiated average VOT values, many younger speakers appear to have neutralized this difference, producing VOTs for aspirated stops that are substantially shorter than those of older speakers, and comparable to those for corresponding lax stops. The data further indicate that, within each age group, older speakers manifest sex-based differences in VOT while younger speakers do not. Despite this appar-ent shift in VOT values, the acoustic evidence suggests that all speakers in this study, regardless of age, continue to mark underlying differences between aspirated and lax stops in terms of stop closure and the fundamental frequency of the following vowel. It is concluded that the data point to a recent phonetic shift in the language, whereby VOT no longer serves as the primary cue to differentiate between lax and aspirated stops. There is not, however, evidence of any reorganization of the lan-guage as the phonemic level: the language's underlying lax ~ aspirated ~ tense contrasts endure.

The effect of voice onset time differences on lexical access in dutch.

Effects on spoken-word recognition of prevoicing differences in Dutch initial voiced plosives were examined. In 2 cross-modal identity-priming experiments, participants heard prime words and nonwords beginning with voiced plosives with 12, 6, or 0 periods of prevoicing or matched items beginning with voiceless plosives and made lexical decisions to visual tokens of those items. Six-period primes had the same effect as 12-period primes. Zero-period primes had a different effect, but only when their voiceless counterparts were real words. Listeners could nevertheless discriminate the 6-period primes from the 12- and 0-period primes. Phonetic detail appears to influence lexical access only to the extent that it is useful: In Dutch, presence versus absence of prevoicing is more informative than amount of prevoicing.

The Perception of Voice Onset Time: An fMRI Investigation of Phonetic Category Structure

This study explored the neural systems underlying the perception of phonetic category structure by investigating the perception of a voice onset time (VOT) continuum in a phonetic categorization task. Stimuli consisted of five synthetic speech stimuli which ranged in VOT from 0 msec ([da]) to 40 msec ([ta]). Results from 12 subjects showed that the neural system is sensitive to VOT differences of 10 msec and that details of phonetic category structure are retained throughout the phonetic processing stream. Both the left inferior frontal gyrus (IFG) and cingulate showed graded activation as a function of category membership with increasing activation as stimuli approached the phonetic category boundary. These results are consistent with the view that the left IFG is involved in phonetic decision processes, with the extent of activation influenced by increased resources devoted to resolving phonetic category membership and/or selecting between competing phonetic categories. Activation patterns in the cingulate suggest that it is sensitive to stimulus difficulty and resolving response conflict. In contrast, activation in the posterior left middle temporal gyrus and the left angular gyrus showed modulation of activation only to the "best fit" of the phonetic category, suggesting that these areas are involved in mapping sound structure to its phonetic representation. The superior temporal gyrus (STG) bilaterally showed weaker sensitivity to the differences in phonetic category structure, providing further evidence that the STG is involved in the early analysis of the sensory properties of speech.

Voice onset time in Mandarin esophageal speech

As an important perceptual cue for voicing and aspiration of stops, voice onset time (VOT) is mainly determined by the aerodynamic interaction between the intraoral and subglottal regions. However, since the PE segment serves as a new vibratory source in esophageal phonation, aerodynamic events are very different from laryngeal phonation. VOT associated with esophageal speech of English has been reported previously. However, few studies have reported VOT characteristics of esophageal speech of tone languages. The present study will investigate the possible VOT difference between esophageal and normal laryngeal speakers of Mandarin Chinese. Seven superior esophageal speakers and 7 normal laryngeal speakers will participate in the present investigation. They will be native male speakers of Mandarin Chinese. The participants will produce the syllable /ta/ embedded in a carrier phrase at a comfortable loudness level for three times. VOT values will be measured from a time domain waveform. With reference to a wide-band (300 Hz) spectrogram, VOT will be defined as the release of stop and the first identifiable period of the vocalic portion. An independent sample t-test will be used to determine if VOT values of esophageal and normal laryngeal speakers were significantly different.

Voice onset time and foreign accent detection : are L2 learners better than monolinguals?

Using an audiovisual perception task, two groups of native English listeners (monolinguals, and L2 learners of Spanish) were asked to identify which /p,t,k/ tokens had been produced by native English speakers and which ones by foreigners. The experiment found that self-reported criteria for foreign accent detection tended to be consistent with actual perceptual behavior, and that the L2 learners performed better, both at the group and at the individual level. These results suggest that foreign accent detection is cued by Voice Onset Time differences and taps into both our tacit knowledge of the native segmental norm and our implicit awareness of what constitutes a particular deviation from that norm. Moreover, the results suggest that, contrary to what some have assumed, monolinguals are not necessarily more sensitive to foreign accents than second language learners.

Sex differences in voice onset time: a developmental study of phonetic context effects in British English.

Voice onset time (VOT) data for the plosives /p b t d k g/ in two vowel contexts (/i a/) for 5 groups of 46 boys and girls aged 5; 8 (5 years, 8 months) to 13;2 years were investigated to examine patterns of sex differences. Results indicated that there was some evidence of females displaying longer VOT values than the males. In addition, these were found to be most marked for the data of the 13;2-year olds. Furthermore, the sex differences in the VOT values displayed phonetic context effects. For example, the greatest sex differences were observed for the voiceless plosives, and within the context of the vowel /i/.

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.]

Voice Onset Time production in older Caucasian- and African-Americans

In an earlier study (Ryalls, Zipprer and Baldauff, 1997) significant differences in Voice Onset Time (VOT) production were found between younger males and younger females, as well as between African-American and Caucasian-American speakers. In this study we attempted to replicate these significant effects for gender and ethnic background in a group of older speakers. Participants in this study were healthy normal speakers between 50 and 70 years of age and included 10 African-Americans and 10 Caucasian-Americans with 10 males and 10 females. Speakers in this study produced real words with each of the 6 stop consonants of English (/p/, /t/, /k/; /b/, /d/, /g/) combined with the three extreme vowels (/i/, /a/, /u/) in monosyllabic words ending with a voiceless stop. Each of these 18 stimuli were then read at least five times in random order within a repetition and recorded onto Digital Audio Tape (DAT). The Brown University Laboratory Interactive Speech System (BLISS, Mertus, 1999) was used to display wavef...

Individual talker differences in voice-onset-time.

Individual talkers differ in the acoustic properties of their speech, and at least some of these differences are in acoustic properties relevant for phonetic perception. Recent findings from studies of speech perception have shown that listeners can exploit such differences to facilitate both the recognition of talkers' voices and the recognition of words spoken by familiar talkers. These findings motivate the current study, whose aim is to examine individual talker variation in a particular phonetically-relevant acoustic property, voice-onset-time (VOT). VOT is a temporal property that robustly specifies voicing in stop consonants. From the broad literature involving VOT, it appears that individual talkers differ from one another in their VOT productions. The current study confirmed this finding for eight talkers producing monosyllabic words beginning with voiceless stop consonants. Moreover, when differences in VOT due to variability in speaking rate across the talkers were factored out using hierarchical linear modeling, individual talkers still differed from one another in VOT, though these differences were attenuated. These findings provide evidence that VOT varies systematically from talker to talker and may therefore be one phonetically-relevant acoustic property underlying listeners' capacity to benefit from talker-specific experience.

Gradient effects of within-category phonetic variation on lexical access

In order to determine whether small within-category differences in voice onset time (VOT) affect lexical access, eye movements were monitored as participants indicated which of four pictures was named by spoken stimuli that varied along a 0–40 ms VOT continuum. Within-category differences in VOT resulted in gradient increases in fixations to cross-boundary lexical competitors as VOT approached the category boundary. Thus, fine-grained acoustic/phonetic differences are preserved in patterns of lexical activation for competing lexical candidates and could be used to maximize the efficiency of on-line word recognition.