Changes In Vowel Quality Research Articles

Lexical Stress Identification in Cochlear Implant-Simulated Speech by Non-Native Listeners.

This study investigates whether a presumed difference in the perceptibility of cues to lexical stress in spectro-temporally degraded simulated cochlear implant (CI) speech affects how listeners weight these cues during a lexical stress identification task, specifically in their non-native language. Previous research suggests that in English, listeners predominantly rely on a reduction in vowel quality as a cue to lexical stress. In Dutch, changes in the fundamental frequency (F0) contour seem to have a greater functional weight than the vowel quality contrast. Generally, non-native listeners use the cue-weighting strategies from their native language in the non-native language. Moreover, few studies have suggested that these cues to lexical stress are differently perceptible in spectro-temporally degraded electric hearing, as CI users appear to make more effective use of changes in vowel quality than of changes in the F0 contour as cues to linguistic phenomena. In this study, native Dutch learners of English identified stressed syllables in CI-simulated and non-CI-simulated Dutch and English words that contained changes in the F0 contour and vowel quality as cues to lexical stress. The results indicate that neither the cue-weighting strategies in the native language nor in the non-native language are influenced by the perceptibility of cues in the spectro-temporally degraded speech signal. These results are in contrast to our expectations based on previous research and support the idea that cue weighting is a flexible and transferable process.

The temporal unfolding of register reveals distinct mechanisms at play: A case study of Western Khmer

Register distinctions are a type of suprasegmental contrasts manifested in several acoustic dimensions, e.g., pitch, vowel quality, and voice quality. However, several aspects of register production remain unclear (Brunelle & Kirby, 2016). In this paper, we focus on whether a target laryngeal configuration may be responsible for the multiplicity of acoustic cues to register. We approach this question through a production study of Western Khmer, an Austronesian language spoken in Chanthaburi, Thailand. Data were collected from 19 speakers producing words with modal or breathy register in a carrier sentence. The measurements we took are trajectories of F0, F1, H1*-H2*, and H1*-A1*. Our results show that all cues are significant in distinguishing the two registers, confirming static measurement results in the previous literature (Wayland, 2001). However, a dynamic study of these register cues reveals a dissociation in their temporal alignment. The F1 transitions that mark changes in vowel quality are not aligned with the transitions of H1*-H2* and H1*-A1* that mark changes in voice quality. These findings suggest that separate asynchronous mechanisms may be responsible for the voice quality and vowel quality components of register production.

Vowel Quality and Direction of Stress Shift in a Predictive Model Explaining the Varying Impact of Misplaced Word Stress: Evidence From English

The use of suprasegmental cues to word stress occurs across many languages. Nevertheless, L1 English listeners' pay little attention to suprasegmental word stress cues and evidence shows that segmental cues are more important to L1 English listeners in how words are identified in speech. L1 English listeners assume strong syllables with full vowels mark the beginning of a new word, attempting alternative resegmentations only when this heuristic fails to identify a viable word string. English word stress errors have been shown to severely disrupt processing for both L1 and L2 listeners, but not all word stress errors are equally damaging. Vowel quality and direction of stress shift are thought to be predictors of the intelligibility of non-standard stress pronunciations—but most research so far on this topic has been limited to two-syllable words. The current study uses auditory lexical decision and delayed word identification tasks to test a hypothesized English Word Stress Error Gravity Hierarchy for words of two to five syllables. Results indicate that English word stress errors affect intelligibility most when they introduce concomitant vowel errors, an effect that is somewhat mediated by the direction of stress shift. As a consequence, the relative intelligibility impact of any particular lexical stress error can be predicted by the Hierarchy for both L1 and L2 English listeners. These findings have implications for L1 and L2 English pronunciation research and teaching. For research, our results demonstrate that varied findings about loss of intelligibility are connected to vowel quality changes of word stress errors and that these factors must be accounted for in intelligibility research. For teaching, the results indicate that not all word stress errors are equally important, and that only word stress errors that affect vowel quality should be prioritized.

Perceptual Compensation of Vowel Nasality in Brazilian Portuguese

This study explores the nature of the oral-nasal vowel contrast in Brazilian Portuguese (BP). While vowel nasality is a salient property in the language, scholars differ on whether this property forms the basis of a phonological contrast. The presence of a consonant-like nasal resonance at the right edge of the heavily nasalized vowels (i.e., nasal appendix) leads to an analysis that nasal vowels may be product of a contextual nasalization rule (e.g., Camara Jr 1970, 1971), thus coarticulatory in nature. While most of the literature explores the issue from the perspective of production, the present study analyzes how BP listeners perceive nasal vowels in comparison to oral counterparts. If vowel nasality is coarticulatory, speakers should perceive it as they would other coarticulation; namely, they would perceptually compensate for vowel nasality, attributing the nasality to the nasal consonant element and hearing the vowel as essentially oral (Beddor & Krakow 1999). If the nasality is phonemic, however, it should not induce compensation. A forced-choice comparison task was presented to a group of 43 BP listeners, who had to compare nasality in vowels of paired stimuli with and without the appendix. Results show that participants did not perceptually compensate for vowel nasality. The substance of the contrast lies in the combination of vowel quality changes associated with nasality and the presence of a nasal appendix.

Vowel discrimination asymmetry: The influence of token variability and lexical characteristics

Listeners are more sensitive to changes in vowel quality when a peripheral vowel rather than a central vowel serves as deviant in an oddball paradigm (asymmetry in vowel discrimination). Schwartz et al. (2005) hypothesized that formant focalization in peripheral vowels make them perceptually more salient than central ones. Interestingly, however, a neurophysiological study (García and Froud, 2014) suggested that lexical familiarity may play a role in this perceptual asymmetry. This study investigated whether or not the asymmetry in vowel discrimination is mediated by the lexical characteristics of the stimulus words. Using an oddball paradigm, mismatch negativity (MMN) responses were elicited from adult monolingual American English listeners using naturally-produced American English vowel contrast /ɑ/-/ʌ/ in a real-word pair (Dock/Duck) and a non-word pair (Dop/Dupp). Listeners heard the pairs in two sessions. It was hypothesized that the MMN responses would be observed only when the peripheral vowel /ɑ/ in real words serves as deviant. Preliminary results suggest that MMN responses were observed for /ɑ/ but not for /ʌ/ regardless of the lexical status of the stimulus words. The implications of findings will be discussed in terms of the effects of lexical status of stimulus words and token variability in vowel discrimination.

On The Realization Of Nominal Possession In Mehinaku: A Diachronic Account

The aim of this paper is to furnish a diachronic account of selected aspects of the morphophonology of nominal possession in Mehinaku, an Arawak language spoken in central Brazil. The phenomena explained here include the systematic occurrence of word-final main stress in Absolute and Genitive forms of nouns, the nasalization of stem-final vowels in a subclass of the Genitive forms, and some vowel quality changes in the paradigms of Inalienable nouns that have defied coherent treatment in comparative and historical Arawak studies. The particular developments postulated in this account are supported both by a consideration of the synchronic regularities holding in Mehinaku phonology and by comparative evidence on the development of the Central Branch of the Arawak family to which this language belongs.

Stress processing in Mandarin and Korean second language learners of English

This study examined stress processing among Mandarin and Korean second language learners of English and English monolinguals. While both English and Mandarin have contrastive stress at the word-level, Korean does not. Consequently, Mandarin speakers may have an advantage over Korean speakers in English stress processing, even when matched for their general English proficiency. Experiment 1 assessed participants’ stress encoding ability for nonwords in a short-term memory task. Experiment 2 examined the effect of stress in online word recognition in a lexical decision task by manipulating word frequency, stress location, and vowel quality. The results of both experiments support an advantage for English and Mandarin speakers over Korean speakers in stress processing of real words and nonwords. Only Korean speakers’ lexical judgment of nonwords was modulated by word frequency, suggesting that they do not utilize stress in lexical access. Only English speakers’ word recognition was facilitated by vowel quality changes. These results suggest that the abilities of non-native speakers to process stress in their L2 is influenced by the characteristics of the stress systems in their L1.

Intrinsic vowel F0 and speech rate

A relation between vowel height and F0 such that, other things being equal, F0 is a little higher in a high vowel than a low vowel appears to be a phonetic universal. However, the cause of this relationship remains unclear. An insight might be gained from ways in which the relationship changes under transformations of speech rate. Ten speakers of American English were recorded saying sentences containing words such as ‘‘bead’’ and ‘‘bad’’ at fast and slow rates. For the majority of the subjects the intrinsic F0 difference was greater in fast speech, contrary to expectation. The difference cannot be explained by changes in vowel quality between the conditions.

Canadian Raising, Opacity, and Rephonemicization

AbstractCanadian Raising—the phonetic changes in vowel quality and quantity in the diphthongs /ai/ and/ au/ before voiceless consonants—has been of considerable importance to phonological theories ever since Joos (1975). The opaque interaction of Canadian Raising and flapping in words such aswriterconsitutes one of the main arguments for rule ordering in phonology (Chomsky and Halle 1968; Chambers 1975). Recently, Mielke, Armstrong, and Hume (2003) have challenged Joos’s phonemic splitting analysis and have argued that Canadian Raising, rather than being a productive phonological process, is a static lexicalized generalization implemented as a choice between allomorphic variants. A rebuttal to this allomorphic analysis is offered based on evidence that, for some speakers, Canadian Raising productively applies in novel morphological contexts, in language games, and in the phrasal phonology, none of which are amenable to an allomorphic analysis.

Stress and tone in East Slavic dialects

The East Slavic languages have distinctive stress and no contrastive vowel length; the phonetic correlates of word stress are increased vowel duration, intensity and changes in vowel quality. But there are East Slavic dialects with an unusual type of word prosody: word stress is distinctive, yet the immediately pretonic vowel is as long as or longer than the vowel under stress, and there is a fixed tonal contour over the two syllables. I argue that the additional duration in the pretonic syllable is due to a type of stress-to-tone mapping in which a lexical high tone is assigned to the pretonic syllable. Variation across these and other closely related dialects reveals a typology of stress and tone mapping with increasing dependence on intrinsic vowel duration and sonority. The additional vowel length on neutralised/reduced vowels in the immediately pretonic position in some dialects raises questions about the relationship of vowel duration and vowel reduction in East Slavic. The prosody of these East Slavic dialects appears to be typologically unusual in having both lexical stress and non-contrastive tone, and in specifically not aligning high tone with stress.

An atypical case of Foreign Accent Syndrome

A new case of Foreign Accent Syndrome is described. This American woman presented with a British‐ or Australian‐ sounding accent after stroke, which resulted in a lacunar infarct in the left internal capsule. The atypical etiology and apparent changes in lexical use are described. It is hypothesized that an abnormally tense vocal tract posture may account for phonetic changes in vowel quality and a higher average fundamental frequency.

Intelligibility and the Listener: The Role of Lexical Stress

For some 30 years, intelligibility has been recognized as an appropriate goal for pronunciation instruction, yet remarkably little is known about the factors that make a language learner's speech intelligible. Studies have traced correlations between features of nonnative speech and native speakers' intelligibility judgements. They have tended to regard prosody as a global phenomenon and to view intelligibility as primarily a quality of the speaker. The present article focuses on a single prosodic element, lexical stress, and shifts the focus of study to the listener. It draws on findings in psycholinguistics that have rarely been applied to second language (L2) contexts. Groups of listeners were asked to transcribe recorded material in which the variables of lexical stress and vowel quality were manipulated. Recognizing the extent to which English is employed in international contexts, the study contrasted the effect of the variables on native listeners (NLs) with their effect on nonnative listeners (NNLs). NLs and NNLs were found to respond in remarkably similar ways to the problems posed by stress misallocation. For both groups, the extent to which intelligibility was compromised depended greatly on the direction in which stress was shifted and whether changes in vowel quality were involved.

Word-level stress patterns in the academic word list

This paper addresses teachers and researchers of English as a second or foreign language who are interested in speech intelligibility training and/or vocabulary acquisition. The study reports a stress-pattern analysis of the Academic Word List (AWL) as made available by Coxhead [TESOL Quarterly 34 (2000) 213]. To examine the AWL in a new way, we identified patterns of word-level stress in the AWL's 525 headwords and 2454 sublist items, or 2979 polysyllabic academic words in all. The report's final table rank orders 39 patterns of word-level stress. We learned that the first 14 patterns encompass over 90% of the AWL's lexical items, while the remaining 25 patterns are low in frequency of occurrence. Results of our analysis may be coupled with information on word-level stress already available in the literature (e.g., systematic shifts in word-level stress—as well as corresponding changes in vowel quality—due to such phenomena as suffixation, derivational morphology, and other aspects of rule-based pedagogy). The paper's concluding section highlights the importance of introducing English for Academic Purposes (EAP) learners to such pattern phenomena in coordination with the word stress frequency data reported in the study.

Changes in Vowel Quality after Cochlear Implantation

Since auditory feedback is partially restored after cochlear implantation, the aim of the present study was to investigate features of vowels, which reflect improvements in speech production. Ten postlingually deafened subjects (5 male/5 female) were recorded reading a German text before and 3 and 12 months after implantation, respectively. Selected vowels were analysed regarding the fundamental frequency (F₀), the formant frequencies (F₁, F₂, F₃) and the vowel space (difference between F₁ and F₂ in hertz). The F₀ decreased only descriptively after 3 and 12 months, respectively. F₁ of the vowel /e/ was significantly lower after 12 months (411 ± 20 compared to 349 ± 25 Hz, p ≤ 0.05) and for /o/ after 3 months (446 ± 29 compared to 408 ± 31 Hz, p ≤ 0.05) for the male patients: their vowel space also expanded significantly for the vowel /o/ (372 ± 37 compared to 467 ± 32 Hz, p ≤ 0.05) after 12 months. Regained auditory feedback after cochlear implantation had an effect on the improvement of the production of vowels.

Changes in vowel quality in post-lingually deafened cochlear implant users.

The present study addresses the effect of cochlear implantation on vowel production of 20 post-lingually deafened Dutch subjects. All subjects received the Nucleus 22 implant (3 WSP and 17 MSP processors). Speech recordings were made pre-implantation and three and twelve months post-implantation with the implant switched on and off. The first and second formant frequencies were measured for eleven Dutch vowels (monophthongs only) in an h-vowel-t context. Twelve months post-implantation, the results showed an increase in the ranges of the first and second formant frequency covered by the respective vowels when the implant was switched on. The increase in the formant frequency range was most marked for some subjects with a relatively small formant range pre-implantation. Also, at 12 months post-implantation with the implant switched on we found a significant shift of the first and second formant frequency towards the normative values. Moreover, at this time the results showed significantly increased clustering of the respective vowels, suggesting an improvement in the ability to produce phonological contrasts between vowels. Clustering is defined as the ratio of the between-vowel variance of the first and second formant frequency and the within-vowel variance of three tokens of the same vowel.

Teaching acoustic cues of nasal resonance

Acoustic coupling between the oral and nasal cavities results in the addition of pole-zero pairs to the vocal-tract transfer function, which interacts with variations in vocal-tract shaping across different vowels and speakers. Presentation of the myraid of acoustic features associated with nasalization based on vocal-tract models can confuse students with little mathematical background. One successful approach allows students to discover a few established cues via waveform and spectrographic analysis. Broadband spectrograms of students’ productions of ‘‘bead–bean’’ clearly illustrate a nasal murmur (200–300 Hz) and the attenuation of formant frequencies is the nasalized vowel compared to the oral vowel. Another broadband spectrogram is made of the tape-recorded speech of a female speaker of Texan English, exhibiting extreme attenuation in the F1 region. The decreased intensity of the nasalized vowel in ‘‘bean’’ (compared to the oral vowel in ‘‘bead’’) is seen as rounded waveform cycles with lower amplitude using waveform-editing software. Changes in vowel quality due to nasalization can be heard as the students proceed screen-by-screen through the waveform.

Vowel quality changes produced by surrounding tone sequences.

In three experiments, we examined whether energy at the same frequency as one of a vowel's harmonics in the F1 region can be captured by a preceding or following sequence of tones. The position of the /I/-/E/ phoneme boundary along an F1 continuum was used to assess the extent of capture. The first two experiments showed that a sequence of tones at 500 Hz (56-msec duration at 10/sec) can perceptually remove added energy at 500 Hz from a steady vowel (F0 = 125 Hz) that forms part of the sequence. The effect is detectable with one preceding tone, asymptotes with four, and is greater when two tones follow the vowel than when none do. Rising and falling sequences of tones (at 62.5-Hz intervals or at whole-tone intervals) differ in their effect. Falling sequences behave much like constant tones at 500 Hz but with less effect, whereas rising sequences show no evidence of removing the added tone. The second experiment replicated the first and also showed that when the vowel is embedded in a rising or a falling sequence of tones that continue after it, the following tones have no effect. The third experiment suggested that the different effects found with rising versus falling sequences are qualitatively predictable on the basis of the additive effects of their constituent tones rather than by virtue of their contour. The experiments indicated that sequences of repeating tones are much more effective at capturing a harmonic from a vowel than are sequences that follow a simple pattern. This result may reflect the operation of a principle of least commitment in auditory grouping.

Tonogenetic mechanisms in northern Mon-Khmer.

In this paper, tonogenesis in the four languages Northern Kammu, Blang, Hu and U is analyzed. For comparison, register development in Lamet is treated as well. All these languages belong to the Palaungic and Kammuic branches of the Mon-Khmer division of the Austroasiatic language family and are fairly closely related, but they have developed tone or register systems independently of each other. These developments can be explained by universal microprosodic properties of segments, which are used in different ways by the different languages. Tone (or register) development is connected with merger of voiced and voiceless initial consonants in Kammu, Blang and Lamet, with merger of long and short vowels in Hu, and with merger of long and short vowels combined with both initial and final consonant changes and vowel quality changes in U. Thus, the range of microprosodic properties used for tonogenesis is extremely wide in this language group.

Intonation precision of choir singers

Results from two experimental investigations on the acoustics of choirs are reported. The first concerns sound-pressure levels (SPL) inside choirs, and the balance of loudness between a singer’s own voice and the ‘‘reference’’ sound from the rest of the choir. Long-term SPL averages during rehearsals typically gave 80–100 dB, with little variation between choirs or with position in the choir. The fundamental frequency precision of choir singers was found to deteriorate abruptly when the reference was too loud. The influence of room acoustics and of the spacing between singers is discussed. The second investigation concerns the effect of spectral variations in the reference sound. Experiments were made primarily with individual singers under laboratory conditions. Changes in vowel quality, and absence/presence of certain partials and of vibrato, were all found to affect somewhat the degree of fundamental frequency agreement between singers. Standard deviation in fundamental frequency between section colleagues in live rehearsal was found to be between 0.10 and 0.15 semitones, or 0.6% and 0.9%. Reference vowels with common partials reinforced by formants were found to increase fundamental frequency precision.

Perception of vowel quality in the presence of other sound sources

If the energy of a harmonic (500 Hz) near the first formant of a vowel is increased, the vowel quality changes. But if the tone corresponding to this increase in energy starts or stops at a different time from the original vowel, then listeners can perceive the original vowel quality [Darwin, Attention and Performance, Vol. X (Erlbaum, 1983)] even though the spectrum present during the vowel is inappropriate. Listeners apparently partition the total sound present into separate percepts on the basis of onset‐ and offset‐time differences. The present experiments show that the same partitioning still occurs when the “original” vowel has reduced energy at 500 Hz. Now adding extra energy to it restores a normal vowel spectrum. Listeners report a vowel quality corresponding to the “original” depleted vowel when the additional energy starts or stops at a different time from the rest of the vowel, even though the spectrum present during the vowel is appropriate to a vowel with a normal spectral envelope. The partitioning of sound sources observed here cannot be explained by a tendency to perceive vowels with conventional spectral envelopes. [Work supported by SERC.]