Acoustic characteristics of English lexical stress produced by native Mandarin speakers

Native speakers of Mandarin Chinese have difficulty producing native-like English stress contrasts. Acoustically, English lexical stress is multidimensional, involving manipulation of fundamental frequency (F0), duration, intensity and vowel quality. Errors in any or all of these correlates could interfere with perception of the stress contrast, but it is unknown which correlates are most problematic for Mandarin speakers. This study compares the use of these correlates in the production of lexical stress contrasts by 10 Mandarin and 10 native English speakers. Results showed that Mandarin speakers produced significantly less native-like stress patterns, although they did use all four acoustic correlates to distinguish stressed from unstressed syllables. Mandarin and English speakers' use of amplitude and duration were comparable for both stressed and unstressed syllables, but Mandarin speakers produced stressed syllables with a higher F0 than English speakers. There were also significant differences in formant patterns across groups, such that Mandarin speakers produced English-like vowel reduction in certain unstressed syllables, but not in others. Results suggest that Mandarin speakers' production of lexical stress contrasts in English is influenced partly by native-language experience with Mandarin lexical tones, and partly by similarities and differences between Mandarin and English vowel inventories.     

Reacquisition of contrastive stress in an adventitiously deaf speaker using a single-channel cochlear implant

Acoustic correlates of contrastive stress, i.e., fundamental frequency (F0), duration, and intensity, and listener perceptions of stress, were investigated in a profoundly deaf subject (RS) pre/post single-channel cochlear implant and longitudinally, and compared to the overall patterns of age-peer profoundly deaf (JM) and normally hearing subjects (DL). The stimuli were a group of general American English words in which a change of function from noun to verb is associated with a shift of stress from initial to final syllable, e.g., CON'trast versus conTRAST'. Precochlear implant, RS was unable to produce contrastive stress correctly. Hearing one day post-stimulation resulted in significantly higher F0 for initial and final stressed versus unstressed syllables. Four months post-stimulation, RS maintained significantly higher F0 on stressed syllables, as well as generalization of significantly increased intensity and longer syllable duration differences for all stressed versus unstressed syllables. Perceptually, listeners judged RS's contrastive stress placement as incorrect precochlear implant and as always correct post-cochlear implant. JM's contrastive stress was judged as 96% correct, and DL's contrastive stress placement was 100% correct. It was concluded that RS reacquired all acoustic correlates needed for appropriate differentiation of contrastive stress with longitudinal use of the cochlear implant.     

Acoustic characteristics of Mandarin esophageal speech

The present study attempted to investigate the acoustic characteristics of Mandarin laryngeal and esophageal speech. Eight normal laryngeal and seven esophageal speakers participated in the acoustic experiments. Results from acoustic analyses of syllables /ma/and /ba/ indicated that, F0, intensity, and signal-to-noise ratio of laryngeal speech were significantly higher than those of esophageal speech. However, opposite results were found for vowel duration, jitter, and shimmer. Mean F0, intensity, and word per minute in reading were greater but number of pauses was smaller in laryngeal speech than those in esophageal speech. Similar patterns of F0 contours and vowel duration as a function of tone were found between laryngeal and esophageal speakers. Long-time spectra analysis indicated that higher first and second formant frequencies were associated with esophageal speech than that with normal laryngeal speech.     

Production of the word-final English /t/-/d/ contrast by native speakers of English, Mandarin, and Spanish.

The primary aim of this study was to determine if adults whose native language permits neither voiced nor voiceless stops to occur in word-final position can master the English word-final /t/-/d/ contrast. Native English-speaking listeners identified the voicing feature in word-final stops produced by talkers in five groups: native speakers of English, experienced and inexperienced native Spanish speakers of English, and experienced and inexperienced native Mandarin speakers of English. Contrary to hypothesis, the experienced second language (L2) learners' stops were not identified significantly better than stops produced by the inexperienced L2 learners; and their stops were correctly identified significantly less often than stops produced by the native English speakers. Acoustic analyses revealed that the native English speakers made vowels significantly longer before /d/ than /t/, produced /t/-final words with a higher F1 offset frequency than /d/-final words, produced more closure voicing in /d/ than /t/, and sustained closure longer for /t/ than /d/. The L2 learners produced the same kinds of acoustic differences between /t/ and /d/, but theirs were usually of significantly smaller magnitude. Taken together, the results suggest that only a few of the 40 L2 learners examined in the present study had mastered the English word-final /t/-/d/ contrast. Several possible explanations for this negative finding are presented. Multiple regression analyses revealed that the native English listeners made perceptual use of the small, albeit significant, vowel duration differences produced in minimal pairs by the nonnative speakers. A significantly stronger correlation existed between vowel duration differences and the listeners' identifications of final stops in minimal pairs when the perceptual judgments were obtained in an "edited" condition (where post-vocalic cues were removed) than in a "full cue" condition. This suggested that listeners may modify their identification of stops based on the availability of acoustic cues.     

The effects of tones on speaking frequency and intensity ranges in Mandarin and Min dialects

The differences of speaking frequency and intensity in different tonal dialects has not been widely investigated. The purposes of this study were (1) to compare the speaking frequency and speaking intensity ranges of Mandarin and Min and (2) to compare the speaking frequency and intensity ranges of Mandarin and Min to those of American English. The subjects were 80 normal Taiwanese adults divided into two dialect groups, Mandarin and Min. The speaking F0, the highest speaking F0, the lowest speaking F0, the maximum range of speaking F0, and the intensity counterpart were obtained from reading in their native dialects. Statistical analysis revealed that Min speakers had a significantly greater maximum range of speaking intensity and a smaller lowest speaking intensity than Mandarin speakers, which indicated tonal effects by speakers of the Min dialect. Moreover, Mandarin and Min speakers had a greater maximum range of speaking F0 and maximum range of speaking intensity than American English speakers. The data may provide an assessment tool for Mandarin speakers and Min speakers.     

Effects of stress and final-consonant voicing on vowel production: articulatory and acoustic analyses

Durations of the vocalic portions of speech are influenced by a large number of linguistic and nonlinguistic factors (e.g., stress and speaking rate). However, each factor affecting vowel duration may influence articulation in a unique manner. The present study examined the effects of stress and final-consonant voicing on the detailed structure of articulatory and acoustic patterns in consonant-vowel-consonant (CVC) utterances. Jaw movement trajectories and F 1 trajectories were examined for a corpus of utterances differing in stress and final-consonant voicing. Jaw lowering and raising gestures were more rapid, longer in duration, and spatially more extensive for stressed versus unstressed utterances. At the acoustic level, stressed utterances showed more rapid initial F 1 transitions and more extreme F 1 steady-state frequencies than unstressed utterances. In contrast to the results obtained in the analysis of stress, decreases in vowel duration due to devoicing did not result in a reduction in the velocity or spatial extent of the articulatory gestures. Similarly, at the acoustic level, the reductions in formant transition slopes and steady-state frequencies demonstrated by the shorter, unstressed utterances did not occur for the shorter, voiceless utterances. The results demonstrate that stress-related and voicing-related changes in vowel duration are accomplished by separate and distinct changes in speech production with observable consequences at both the articulatory and acoustic levels.     

Simultaneous effects on vowel duration in American English: a covariance structure modeling approach

The powerful techniques of covariance structure modeling (CSM) long have been used to study complex behavioral phenomenon in the social and behavioral sciences. This study employed these same techniques to examine simultaneous effects on vowel duration in American English. Additionally, this study investigated whether a single population model of vowel duration fits observed data better than a dual population model where separate parameters are generated for syllables that carry large information loads and for syllables that specify linguistic relationships. For the single population model, intrinsic duration, phrase final position, lexical stress, post-vocalic consonant voicing, and position in word all were significant predictors of vowel duration. However, the dual population model, in which separate model parameters were generated for (1) monosyllabic content words and lexically stressed syllables and (2) monosyllabic function words and lexically unstressed syllables, fit the data better than the single population model. Intrinsic duration and phrase final position affected duration similarly for both the populations. On the other hand, the effects of post-vocalic consonant voicing and position in word, while significant predictors of vowel duration in content words and stressed syllables, were not significant predictors of vowel duration in function words or unstressed syllables. These results are not unexpected, based on previous research, and suggest that covariance structure analysis can be used as a complementary technique in linguistic and phonetic research.     

Multimodal Standardization of Voice Among Four Multicultural Populations Formant Structures

A stratified random sample of 20 males and 20 females matched for physiologic factors and cultural-linguistic markers was examined to determine differences in formant frequencies during prolongation of three vowels: [a], [i], and [u]. The ethnic and gender breakdown included four sets of 5 male and 5 female subjects comprised of Caucasian and African American speakers of Standard American English, native Hindi Indian speakers, and native Mandarin Chinese speakers. Acoustic measures were analyzed using the Computerized Speech Lab (4300B) from which formant histories were extracted from a 200-ms sample of each vowel token to obtain first formant (F1), second formant (F2), and third formant (F3) frequencies. Significant group differences for the main effect of culture and race were found. For the main effect gender, sexual dimorphism in vowel formants was evidenced for all cultures and races across all three vowels. The acoustic differences found are attributed to cultural-linguistic factors.     

Effect of tonal native language on voice fundamental frequency responses to pitch feedback perturbations during sustained vocalizations

The purpose of this cross-language study was to examine whether the online control of voice fundamental frequency (F(0)) during vowel phonation is influenced by language experience. Native speakers of Cantonese and Mandarin, both tonal languages spoken in China, participated in the experiments. Subjects were asked to vocalize a vowel sound /u/at their comfortable habitual F(0), during which their voice pitch was unexpectedly shifted (± 50, ± 100, ± 200, or ± 500 cents, 200 ms duration) and fed back instantaneously to them over headphones. The results showed that Cantonese speakers produced significantly smaller responses than Mandarin speakers when the stimulus magnitude varied from 200 to 500 cents. Further, response magnitudes decreased along with the increase in stimulus magnitude in Cantonese speakers, which was not observed in Mandarin speakers. These findings suggest that online control of voice F(0) during vocalization is sensitive to language experience. Further, systematic modulations of vocal responses across stimulus magnitude were observed in Cantonese speakers but not in Mandarin speakers, which indicates that this highly automatic feedback mechanism is sensitive to the specific tonal system of each language.     

Perceiving unstressed vowels in foreign-accented English

This paper investigated how foreign-accented stress cues affect on-line speech comprehension in British speakers of English. While unstressed English vowels are usually reduced to /?/, Dutch speakers of English only slightly centralize them. Speakers of both languages differentiate stress by suprasegmentals (duration and intensity). In a cross-modal priming experiment, English listeners heard sentences ending in monosyllabic prime fragments--produced by either an English or a Dutch speaker of English--and performed lexical decisions on visual targets. Primes were either stress-matching ("ab" excised from absurd), stress-mismatching ("ab" from absence), or unrelated ("pro" from profound) with respect to the target (e.g., ABSURD). Results showed a priming effect for stress-matching primes only when produced by the English speaker, suggesting that vowel quality is a more important cue to word stress than suprasegmental information. Furthermore, for visual targets with word-initial secondary stress that do not require vowel reduction (e.g., CAMPAIGN), resembling the Dutch way of realizing stress, there was a priming effect for both speakers. Hence, our data suggest that Dutch-accented English is not harder to understand in general, but it is in instances where the language-specific implementation of lexical stress differs across languages.     

Temporal characteristics of nasalization in children and adult speakers of American English and Korean during production of three vowel contexts

The purpose of this study was to identify and compare the temporal characteristics of nasalization in relation to (1) languages, (2) vowel contexts, and (3) age groups. Two distinct acoustic energies from the mouth and nose were recorded during speech production (/pamap, pimip, pumup/) using two microphones to obtain the absolute and proportional measurements on the acoustic temporal characteristics of nasalization. Twenty-eight normal adults (14 American English and 14 Korean speakers) and 28 normal children (14 American English and 14 Korean speakers) participated in this study. In both languages, adults showed shorter duration of nasalization than children within all three vowel contexts. The high vowel context revealed longer duration of nasalization than the low vowel context in both languages. There was no significant difference of temporal characteristics of nasalization between American English and Korean. Nasalization showed different timing characteristics between children and adults across vowel contexts. The results are discussed in association with developmental coarticulation and the relationship between acoustic consequences of articulatory events and vowel height.     

Habitual use of vocal fry in young adult female speakers

The purpose of this study was to examine the use of vocal fry in young adult Standard American-English (SAE) speakers. This was a preliminary attempt (1) to determine the prevalence of the use of this register in young adult college-aged American speakers and (2) to describe the acoustic characteristics of vocal fry in these speakers. Subjects were 34 female college students. They were native SAE speakers aged 18-25 years. Data collection procedures included high quality recordings of two speaking conditions, (1) sustained isolated vowel /a/ and (2) sentence reading task. Data analyses included both perceptual and acoustic evaluations. Results showed that approximately two-thirds of this population used vocal fry and that it was most likely to occur at the end of sentences. In addition, statistically significant differences between vocal fry and normal register were found for mean F(0) minimum, F(0) maximum, F(0) range, and jitter local. Preliminary findings were taken to suggest that use of the vocal fry register may be common in some adult SAE speakers.     

Effect of speaking rate on vowel formant movements

The purpose of this experiment was to study the effects of changes in speaking rate on both the attainment of acoustic vowel targets and the relative time and speed of movements toward these presumed targets. Four speakers produced a number of different CVC and CVCVC utterances at slow and fast speaking rates. Spectrographic measurements showed that the midpoint format frequencies of the different vowels did not vary as a function of rate. However, for fast speech the onset frequencies of second formant transitions were closer to their target frequencies while CV transition rates remained essentially unchanged, indicating that movement toward the vowel simply began earlier for fast speech. Changes in both speaking rate and lexical stress had different effects. For stressed vowels, an increase in speaking rate was accompanied primarily by a decrease in duration. However, destressed vowels, even if they were of the same duration as quickly produced stressed vowels, were reduced in overall amplitude, fundamental frequency, and to some extent, vowel color. These results suggest that speaking rate and lexical stress are controlled by two different mechanisms.     

Comparison of speaking fundamental frequency in English and Mandarin

To determine if the speaking fundamental frequency (F0) profiles of English and Mandarin differ, a variety of voice samples from male and female speakers were compared. The two languages' F0 profiles were sometimes found to differ, but these differences depended on the particular speech samples being compared. Most notably, the physiological F0 ranges of the speakers, determined from tone sweeps, hardly differed between the two languages, indicating that the English and Mandarin speakers' voices are comparable. Their use of F0 in single-word utterances was, however, quite different, with the Mandarin speakers having higher maximums and means, and larger ranges, even when only the Mandarin high falling tone was compared with English. In contrast, for a prose passage, the two languages were more similar, differing only in the mean F0, Mandarin again being higher. The study thus contributes to the growing literature showing that languages can differ in their F0 profile, but highlights the fact that the choice of speech materials to compare can be critical.     

Target spectral, dynamic spectral, and duration cues in infant perception of German vowels

Previous studies of vowel perception have shown that adult speakers of American English and of North German identify native vowels by exploiting at least three types of acoustic information contained in consonant-vowel-consonant (CVC) syllables: target spectral information reflecting the articulatory target of the vowel, dynamic spectral information reflecting CV- and -VC coarticulation, and duration information. The present study examined the contribution of each of these three types of information to vowel perception in prelingual infants and adults using a discrimination task. Experiment 1 examined German adults' discrimination of four German vowel contrasts (see text), originally produced in /dVt/ syllables, in eight experimental conditions in which the type of vowel information was manipulated. Experiment 2 examined German-learning infants' discrimination of the same vowel contrasts using a comparable procedure. The results show that German adults and German-learning infants appear able to use either dynamic spectral information or target spectral information to discriminate contrasting vowels. With respect to duration information, the removal of this cue selectively affected the discriminability of two of the vowel contrasts for adults. However, for infants, removal of contrastive duration information had a larger effect on the discrimination of all contrasts tested.     

Separability of prosodic phrase boundary and phonemic information

It was hypothesized that the retrieval of prosodic and phonemic information from the acoustic signal is facilitated when prosodic information is encoded by co-occurring suprasegmental cues. To test the hypothesis, two-choice speeded classification experiments were conducted, which examined processing interaction between prosodic phrase-boundary vs stop-place information in speakers of Southern British English. Results confirmed that the degree of interaction between boundary and stop-place information diminished when the pre-boundary vowel was signaled by duration and F(0), compared to when it was signaled by either duration or F(0) alone. It is argued that the relative ease of retrieval of prosodic and phonemic information arose from advantages of prosodic cue integration.     

Production of phonetic and phonological contrast by heritage speakers of Mandarin

This study tested the hypothesis that heritage speakers of a minority language, due to their childhood experience with two languages, would outperform late learners in producing contrast: language-internal phonological contrast, as well as cross-linguistic phonetic contrast between similar, yet acoustically distinct, categories of different languages. To this end, production of Mandarin and English by heritage speakers of Mandarin was compared to that of native Mandarin speakers and native American English-speaking late learners of Mandarin in three experiments. In experiment 1, back vowels in Mandarin and English were produced distinctly by all groups, but the greatest separation between similar vowels was achieved by heritage speakers. In experiment 2, Mandarin aspirated and English voiceless plosives were produced distinctly by native Mandarin speakers and heritage speakers, who both put more distance between them than late learners. In experiment 3, the Mandarin retroflex and English palato-alveolar fricatives were distinguished by more heritage speakers and late learners than native Mandarin speakers. Thus, overall the hypothesis was supported: across experiments, heritage speakers were found to be the most successful at simultaneously maintaining language-internal and cross-linguistic contrasts, a result that may stem from a close approximation of phonetic norms that occurs during early exposure to both languages.     

Multimodal Standardization of Voice Among Four Multicultural Populations: Fundamental Frequency and Spectral Characteristics

A stratified random sample of 20 males and 20 females matched for physiological factors and cultural-linguistic markers were examined to determine differences in fundamental frequency and spectral characteristics during prolongation of three vowels: [a], [i], and [u]. The ethnic-gender breakdown included four sets of five male and five female subjects comprised of Caucasian and African-American speakers of standard American English, native Hindi Indian speakers, and native Mandarin Chinese speakers. Acoustic measures were analyzed using the Multidimensional Voice Program (Kay Elemetrics, Lincoln Park, NJ) (Model 4305) from which fundamental frequency and associated acoustic spectra were extracted from a 200-ms sample of each vowel token. Statistically significant group differences for the main effects of culture, race, and gender were found. The acoustic differences found are attributed to biomechanical, physiological, cultural, and linguistic factors.     

Intrinsic fundamental frequency of vowels in sentence context

High vowels have a higher intrinsic fundamental frequency (F0) than low vowels. This phenomenon has been verified in several languages. However, most studies of intrinsic F0 of vowels have used words either in isolation or bearing the main phrasal stress in a carrier sentence. As a first step towards an understanding of how the intrinsic F0 of vowels interacts with intonation in running speech, this study examined F0 of the vowels [i,a,u] in four sentence positions. The four speakers used for this study showed a statistically significant main effect of intrinsic F0 (high vowels had higher F0). Three of the four speakers also showed an interaction between intrinsic F0 and sentence position such that no significant F0 difference was observed in the unaccented, sentence-final position. The interaction was shown not to be due to vowel neutralization or correlated with changes in the glottal waveform shape, as evidenced by measures of the first formant frequency and spectral slope. Comparison with studies of tone languages and speech of the deaf suggests that both the lack of accent and the lower F0 caused the reduction in the intrinsic F0 difference.     

Acoustic effects of variation in vocal effort by men, women, and children

The acoustic effects of the adjustment in vocal effort that is required when the distance between speaker and addressee is varied over a large range (0.3-187.5 m) were investigated in phonated and, at shorter distances, also in whispered speech. Several characteristics were studied in the same sentence produced by men, women, and 7-year-old boys and girls: duration of vowels and consonants, pausing and occurrence of creaky voice, mean and range of F0, certain formant frequencies (F1 in [a] and F3), sound-pressure level (SPL) of voiced segments and [s], and spectral emphasis. In addition to levels and emphasis, vowel duration, F0, and F1 were substantially affected. "Vocal effort" was defined as the communication distance estimated by a group of listeners for each utterance. Most of the observed effects correlated better with this measure than with the actual distance, since some additional factors affected the speakers' choice. Differences between speaker groups emerged in segment durations, pausing behavior, and in the extent to which the SPL of [s] was affected. The whispered versions are compared with the phonated versions produced by the same speakers at the same distance. Several effects of whispering are found to be similar to those of increasing vocal effort.