Acoustic characteristics of clearly spoken English tense and lax vowels

Acoustic analysis of English tense and lax vowels: Comparing the production between Mandarin Chinese learners and native English speakers

This study investigated how 40 Chinese learners of English as a foreign language (EFL learners) differed from 40 native English speakers in the production of four English tense-lax contrasts, /i-ɪ/, /u-ʊ/, /ɑ-ʌ/, and /æ-ε/, by examining the acoustic measurements of duration, the first three formant frequencies, and the slope of the first formant movement (F1 slope). The dynamic formant trajectory was modeled using discrete cosine transform coefficients to demonstrate the time-varying properties of formant trajectories. A discriminant analysis was employed to illustrate the extent to which Chinese EFL learners relied on different acoustic parameters. This study found that: (1) Chinese EFL learners overemphasized durational differences and weakened spectral differences for the /i-ɪ/, /u-ʊ/, and /ɑ-ʌ/ pairs, although they maintained sufficient spectral differences for /æ-ε/. In contrast, native English speakers predominantly used spectral differences across all four pairs; (2) in non-low tense-lax contrasts, unlike native English speakers, Chinese EFL learners failed to exhibit different F1 slope values, indicating a non-nativelike tongue-root placement during the articulatory process. The findings underscore the contribution of dynamic spectral patterns to the differentiation between English tense and lax vowels, and reveal the influence of precise articulatory gestures on the realization of the tense-lax contrast.

Within-talker and within-session stability of acoustic characteristics of conversational and clear speaking stylesa)

In speech production research, talkers often perform a speech task several times per recording session with different speaking styles or in different environments. For example, Lombard speech studies typically have talkers speak in several different noise conditions. However, it is unknown to what degree simple repetition of a speech task affects speech acoustic characteristics or whether repetition effects might offset or exaggerate effects of speaking style or environment. The present study assessed speech acoustic changes over four within-session repetitions of a speech production taskset performed with two speaking styles recorded in separate sessions: conversational and clear speech. In each style, ten talkers performed a set of three speech tasks four times. Speaking rate, median fundamental frequency, fundamental frequency range, and mid-frequency spectral energy for read sentences were measured and compared across test blocks both within-session and between the two styles. Results indicate that statistically significant changes can occur from one repetition of a speech task to the next, even with a brief practice set and especially in the conversational style. While these changes were smaller than speaking style differences, these findings support using a complete speech set for training while talkers acclimate to the task and to the laboratory environment.

Multi-modal cross-linguistic perception of Mandarin tones in clear speech

Clearly enunciated speech (relative to conversational, plain speech) involves articulatory and acoustic modifications that enhance auditory-visual (AV) segmental intelligibility. However, little research has explored clear-speech effects on the perception of suprasegmental properties such as lexical tone, particularly involving visual (facial) perception. Since tone production does not primarily rely on vocal tract configurations, tones may be less visually distinctive. Questions thus arise as to whether clear speech can enhance visual tone intelligibility, and if so, whether any intelligibility gain can be attributable to tone-specific category-enhancing (code-based) clear-speech cues or tone-general saliency-enhancing (signal-based) cues. The present study addresses these questions by examining the identification of clear and plain Mandarin tones with visual-only, auditory-only, and AV input modalities by native (Mandarin) and nonnative (English) perceivers. Results show that code-based visual and acoustic clear tone modifications, although limited, affect both native and nonnative intelligibility, with category-enhancing cues increasing intelligibility and category-blurring cues decreasing intelligibility. In contrast, signal-based cues, which are extensively available, do not benefit native intelligibility, although they contribute to nonnative intelligibility gain. These findings demonstrate that linguistically relevant visual tonal cues are existent. In clear speech, such tone category-enhancing cues are incorporated with saliency-enhancing cues across AV modalities for intelligibility improvements.

Plain-to-clear speech video conversion for enhanced intelligibility

Clearly articulated speech, relative to plain-style speech, has been shown to improve intelligibility. We examine if visible speech cues in video only can be systematically modified to enhance clear-speech visual features and improve intelligibility. We extract clear-speech visual features of English words varying in vowels produced by multiple male and female talkers. Via a frame-by-frame image-warping based video generation method with a controllable parameter (displacement factor), we apply the extracted clear-speech visual features to videos of plain speech to synthesize clear speech videos. We evaluate the generated videos using a robust, state of the art AI Lip Reader as well as human intelligibility testing. The contributions of this study are: (1) we successfully extract relevant visual cues for video modifications across speech styles, and have achieved enhanced intelligibility for AI; (2) this work suggests that universal talker-independent clear-speech features may be utilized to modify any talker's visual speech style; (3) we introduce "displacement factor" as a way of systematically scaling the magnitude of displacement modifications between speech styles; and (4) the high definition generated videos make them ideal candidates for human-centric intelligibility and perceptual training studies.

Non-native talkers and listeners and the perceptual benefits of clear speech

This study examined the intelligibility benefit of native and non-native clear speech for native and non-native listeners when the first language background of non-native talkers and listeners is matched. All four combinations of talkers and listeners were tested: native talker-native listener, non-native talker-native listener, native talker-non-native listener, and non-native talker-non-native listener. Listeners were presented with structurally simple but semantically anomalous English sentences produced clearly or casually and mixed with speech-shaped noise at 0 dB signal-to-noise ratio and asked to write down what they heard. Results showed that native English speech was more intelligible than non-native speech and that native English listeners recovered speech better than non-native listeners did. Clear speech was significantly more intelligible than casual speech. There were no interactions between speaking style and native language background indicating that clear speech intelligibility benefit was not significantly different across distinct combinations of talkers and listeners. In particular, shared first language background among non-native speakers and listeners did not provide an extra benefit in either the overall speech intelligibility or the intelligibility gains of clear speech.

Clear speech in Tashlhiyt Berber: The perception of typologically uncommon word-initial contrasts by native and naive listeners

Tashlhiyt Berber is known for having typologically unusual word-initial phonological contrasts, specifically, word-initial singleton-geminate minimal pairs (e.g., sin vs ssin) and sequences of consonants that violate the sonority sequencing principle (e.g., non-rising sonority sequences: fsin). The current study investigates the role of a listener-oriented speaking style on the perceptual enhancement of these rarer phonological contrasts. It examines the perception of word-initial singleton, geminate, and complex onsets in Tashlhiyt Berber across clear and casual speaking styles by native and naive listeners. While clear speech boosts the discriminability of pairs containing singleton-initial words for both listener groups, only native listeners performed better in discriminating between initial singleton-geminate contrasts in clear speech. Clear speech did not improve perception for lexical contrasts containing a non-rising-sonority consonant cluster for either listener group. These results are discussed in terms of how clear speech can inform phonological typology and the role of phonetic enhancement in language-universal vs language-specific speech perception.

Training the pronunciation of L2 vowels under different conditions: the use of non-lexical materials and masking noise

The current study extends traditional perceptual high-variability phonetic training (HVPT) in a foreign language learning context by implementing a comprehensive training paradigm that combines perception (discrimination and identification) and production (immediate repetition) training tasks and by exploring two potentially enhancing training conditions: the use of non-lexical training stimuli and the presence of masking noise during production training. We assessed training effects on L1-Spanish/Catalan bilingual EFL learners' production of a difficult English vowel contrast (/æ/-/ʌ/). The participants (N = 62) were randomly assigned to either non-lexical (N = 24) or lexical (N = 24) training and were further subdivided into two groups, one trained in noise (N = 12) and one in silence (N = 12). An untrained control group (N = 14) was also tested. Training gains, measured through spectral distance scores (Euclidean distances) with respect to native speakers' productions of /æ/ and /ʌ/, were assessed through delayed word and sentence repetition tasks. The results showed an advantage of non-lexical training over lexical training, detrimental effects of noise for participants trained with nonwords, but not for those trained with words, and less accurate production of vowels elicited in isolated words than in words embedded in sentences, where training gains were only observable for participants trained with nonwords.

The contrast between clear and plain speaking style for Mandarin tones

We examine the acoustic characteristics of clear and plain conversational productions of Mandarin tones. Twenty-one native Mandarin speakers were asked to produce a selection of Mandarin words in both plain and clear speaking styles. Several tokens were gathered for each of the four tones giving a total of 2045 productions. Six critical tonal cues were computed for each production: fundamental frequency (F0) mean, slope, and second derivative, duration, mean intensity, and a binary variable coding whether the production involved creaky voice. A linear mixed-effects regression model was used to explore how these cues changed with respect to the clear versus plain distinction for each tone, with speaking style as the fixed effect and speaker being a random effect. The strongest effects detected were that duration and mean intensity increased in clear speech across speakers and tones. Tones 2 and 3 increased in mean F0 and Tone 4 increased its slope. An additional finding was that, for contour tones, speakers accomplished the increase in duration by stretching out the tone contours in time while largely not changing the F0 range. These results are discussed in terms of signal-based (affecting all tones) and code-based (enhancing contrast between tones) change.

The Role of the Speaker, the Listener, and Their Joint Contributions During Communicative Interactions: A Tripartite View of Intelligibility in Individuals With Dysarthria

Purpose We present a tripartite view of intelligibility in which the contributions of both the speaker and listener, as well as their joint effort during interaction, are considered. While considerable research has examined communicative interactions in situ, there is a critical gap in current knowledge on how speech intelligibility unfolds during such interactions. Here, we argue that research examining speech intelligibility in communicative interactions may provide important groundwork for advancement in clinical interventions for individuals with dysarthria. Method First, we describe the view and argue for its consideration as a powerful way of thinking about speech intelligibility. We then briefly situate the view in the relevant literature on speech intelligibility and existing theoretical frameworks. We then identify suitable methodological paradigms for studying joint contributions to intelligibility and, lastly, discuss the clinical application and potential impact of this tripartite view. Conclusions Speech communication occurs through interaction; however, in the laboratory and clinic, emphasis is usually placed on individual speakers and listeners. We have proposed that it is critical to consider how the joint contributions of speakers and listeners affect speech intelligibility in communicative interaction. This conceptualization is well aligned with the International Classification of Functioning, Disability and Health, and the findings from such an approach will allow us to better understand how to maximize available resources to enhance speech intelligibility.

Multi-modal cross-linguistic perception of fricatives in clear speech

Research shows that acoustic modifications in clearly enunciated fricative consonants (relative to the plain, conversational productions) facilitate auditory fricative perception, particularly for auditorily salient sibilant fricatives and for native perception. However, clear-speech effects on visual fricative perception have received less attention. A comparison of auditory and visual (facial) clear-fricative perception is particularly interesting since sibilant fricatives in English are more auditorily salient while non-sibilants are more visually salient. This study thus examines clear-speech effects on multi-modal perception of English sibilant and non-sibilant fricatives. Native English perceivers and non-native (Mandarin, Korean) perceivers with different fricative inventories in their native languages (L1s) identified clear and conversational fricative-vowel syllables in audio-only, visual-only, and audio-visual (AV) modes. The results reveal an overall positive clear-speech effect when visual information is involved. Considering the factor of AV saliency, clear speech benefits sibilants more in the auditory domain and non-sibilants more in the visual domain. With respect to language background, non-native (Mandarin and Korean) perceivers benefit from visual as well as auditory information, even for fricatives non-existent in their respective L1s, but the patterns of clear-speech gains are affected by the relative AV weighting and "nativeness" of the fricatives. These findings are discussed in terms of how saliency-enhancing and category-distinctive cues of speech sounds are adopted in AV perception to improve intelligibility.

Acoustic characteristics of tense and lax vowels across sentence position in clear speech

This study examines how the inherent properties of tense and lax vowels interact with external factors, such as speech style (clear vs conversational) and position (sentence-medial vs sentence-final). Twelve speakers of American English recorded productions of the tense /i,u,ɑ/ and lax /ɪ,ɛ,æ,ʊ,ʌ/ vowels, all of which were lengthened and decentralized to a similar degree in clear speech. Furthermore, unlike tense vowels, lax vowels had a greater vowel space area in sentence-medial position, which was primarily driven by high vowels' decreased F1. Therefore, the defining properties of lax vowels (short duration and centralization) were altered by both speech style and sentential position.

Regional Variation in Fundamental Frequency of American English Vowels

We examined whether the fundamental frequency (f0) of vowels is influenced by regional variation, aiming to (1) establish how the relationship between vowel height and f0 ("intrinsic f0") is utilized in regional vowel systems and (2) determine whether regional varieties differ in their implementation of the effects of phonetic context on f0 variations. An extended set of acoustic measures explored f0 in vowels in isolated tokens (experiment 1) and in connected speech (experiment 2) from 36 women representing 3 different varieties of American English. Regional differences were found in f0 shape in isolated tokens, in the magnitude of intrinsic f0 difference between high and low vowels, in the nature of f0 contours in stressed vowels, and in the completion of f0 contours in the context of coda voicing. Regional varieties utilize f0 control in vowels in different ways, including regional f0 ranges and variation in f0 shape.

Tongue- and Jaw-Specific Contributions to Acoustic Vowel Contrast Changes in the Diphthong /ai/ in Response to Slow, Loud, and Clear Speech

PURPOSE

This study sought to determine decoupled tongue and jaw displacement changes and their specific contributions to acoustic vowel contrast changes during slow, loud, and clear speech.

METHOD

Twenty typical talkers repeated "see a kite again" 5 times in 4 speech conditions (typical, slow, loud, clear). Speech kinematics were recorded using 3-dimensional electromagnetic articulography. Tongue composite displacement, decoupled tongue displacement, and jaw displacement during /ai/, as well as the distance between /a/ and /i/ in the F1-F2 vowel space, were examined during the diphthong /ai/ in "kite."

RESULTS

Displacements significantly increased during all 3 speech modifications. However, jaw displacements increased significantly more during clear speech than during loud and slow speech, whereas decoupled tongue displacements increased significantly more during slow speech than during clear and loud speech. In addition, decoupled tongue displacements increased significantly more during clear speech than during loud speech. Increases in acoustic vowel contrast tended to be larger during slow speech than during clear speech and were predominantly tongue-driven, whereas those during clear speech were fairly equally accounted for by changes in decoupled tongue and jaw displacements. Increases in acoustic vowel contrast during loud speech were smallest and were predominantly tongue-driven, particularly in men.

CONCLUSIONS

Findings suggest that task-specific patterns of decoupled tongue and jaw displacement change and task-specific patterns of decoupled tongue and jaw contributions to vowel acoustic change across these speech modifications. Clinical implications are discussed.

Estimating Vocal Effort from the Aerodynamics of Labial Fricatives: A Feasibility Study

OBJECTIVE AND HYPOTHESIS

Vocal effort in loud voice is produced with increased subglottal pressure during vowels and increased supraglottal pressure during consonants. In the paper, our main objective is to check whether it was supported by a parallel increase in the airflow resistance of the laryngeal articulator and of the supralaryngeal articulator, here the lips.

STUDY DESIGN AND METHOD

For this comparison, our choice fell on the fricative consonants, as their production allows perfectly synchronous air pressure and airflow measurements. Also, the calculation of the real instantaneous aerodynamic resistance is possible with fricatives-as it is with vowels-whereas it is not possible with plosives. The present feasibility study on a healthy subject is based on direct subglottal and intraoral pressures and airflow measured for /f/ or /v/ and from the contiguous vowel produced in VCVCV nonsense words at different levels of intensity.

RESULTS AND CONCLUSION

The results support that the airflow resistances at the lips and that at the larynx are quite parallel. The airflow resistance at the lips during labial fricative production could provide a good picture of the laryngeal resistance during the production of continuous speech. This suggests clinical applications using both noninvasive inferred measurements of subglottal pressure variation and direct noninferred airflow measurements from more natural speech production tasks.