Effect Of Clear Speech Research Articles

Clear speech effects in production of sentence-medial Mandarin lexical tonesa).

Adding to limited research on clear speech in tone languages, productions of Mandarin lexical tones were examined in pentasyllabic sentences. Fourteen participants read sentences imagining a hard-of-hearing addressee or a friend in a casual social setting. Tones produced in clear speech had longer duration, higher intensity, and larger F0 values. This style effect was rarely modulated by tone, preceding tonal context, or syllable position, consistent with an overall signal enhancement strategy. Possible evidence for tone enhancement was observed only in one set of analysis for F0 minimum and F0 range, contrasting tones with low targets and tones with high targets.

Acoustic adjustments of clear speech in Korean heritage vowel production

Aims and objectives: This study aims to explore the segmental and suprasegmental acoustic adjustments in the clear speech of Korean vowels produced by English-dominant Korean-heritage speakers and native Korean speakers. Methodology: Native Korean students at a university in the United States and Korean-American students enrolled in an intermediate Korean language course at the same university read isolated sentences featuring three representative Korean vowels (i.e., /i, a, u/), once in casual speech, and once in clear speech. They repeated this sequence five times. Data and analysis: The vowel space of the first and second formants (F1 and F2) in the clear speech was expanded for both heritage and native speakers, and the heritage vowel space was more fronted than the native vowel space, suggesting the influence of English among heritage speakers. However, the peripheral extent and direction in the clear speech and the dominant language effect in heritage speakers were inconsistent across the vowels. Also, pitch dynamics were highly significant in clear speech, exhibiting the salient fundamental frequency (F0) rising at the syllable offset for both heritage and native speakers. The vowel length enhancement in the clear speech was also confirmed in both native and heritage Korean vowels. Conclusions: The results confirmed the cross-language tendency in clear speech to induce the modification of vowel quality, pitch, and duration, which also applies to Korean heritage vowel production. Furthermore, the asymmetrical acoustic modifications across the vowels in heritage clear speech support the Speech Learning Model (SLM) prediction. Originality and implications: The findings present new data for the clear speech effects of Korean heritage vowel production and a further enhancement strategy of syllable offset pitch raising in clear speech for both native and heritage groups. The results contribute to the theoretical implication of bilingualism by connecting the SLM premise and heritage clear speech.

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.

Effect of clear speech on acoustic measures of dysprosody in Parkinson disease for different reading tasks

Purpose The purpose of the study was to determine the effect of clear speech instruction on acoustic measures of dysprosody between reading passages of differing linguistic content for speakers with and without Parkinson Disease (PD). Method Ten speakers with PD and 10 controls served as participants and read five simple and three standard reading stimuli twice. First, speakers read habitually and then following clear speech instruction. Acoustic measures of fundamental frequency variation (semitone standard deviation, STSD), articulation rate, and between-complex pause durations were calculated. Result Results indicated speakers with PD exhibited less fundamental frequency variation than controls across reading stimuli and instructions. All speakers exhibited lower STSD and longer between-complex pause durations for the standard compared to simple reading stimuli. For clear speech, all speakers reduced articulation rate and increased between-complex pause durations in both simple and standard reading stimuli. However, speakers with PD exhibited a significantly less robust reduction in articulation rate for clear speech than control speakers for all reading stimuli. Conclusion Linguistic content of reading stimuli contributes to differences in fundamental frequency variation and pause duration for all speakers. All speakers reduced articulation rate for clear speech compared to habitual instruction, but speakers with PD did so to a lesser extent than controls. Linguistic content of reading stimuli to examine dysprosody in PD should be considered for clinical application.

The effect of clear speech to foreign-sounding interlocutors on native listeners’ perception of intelligibility

Hyperarticulation is an acoustic modification of the speech stream that has been reliably shown to be naturally part of clear speech. Despite the large number of studies that have investigated the relationship between clear speech properties (e.g. expanded vowel space) and intelligibility, only an associative, rather than a causal relationship between vowel space expansion and speech intelligibility has been documented to this date.The focus of this study was to more directly explore the impact of vowel hyperarticulation on intelligibility. Specifically, it tested the effect that naturally elicited speech in interaction with native-sounding adults and foreign-sounding adults had on intelligibility. Twenty-one native speakers of English transcribed and provided ratings of typicality and clarity for speech that was produced while speakers were interacting with native-sounding and foreign-sounding adults. Results revealed that speech directed at L2 speakers is more intelligible and rated as being clearer and a more typical representation of speech compared to speech directed at L1 speakers. Implications of the findings are discussed in terms of Lindblom's Hyper-and Hypoarticulation theory (1992).

Clear speech research in dysarthria

A sizeable group of theoretically grounded studies has defined clear speech production for neurotypical talkers as well as the perceptual consequences of neurotypical clear speech. Although less robust in size compared to the neurotypical literature, clear speech research focused on the clinical population of dysarthria has grown substantially over the last decade. The growth stems, in part, from the positive effects of clear speech on intelligibility, a perceptual construct central to the clinical management of dysarthria. We will review dysarthria research from our lab examining the effects of clear speech on speech acoustics and subsequently, on perceptual measures of speech. Factors which may contribute to variability in clear speech outcomes in dysarthria will be considered. These factors include but are not limited to (1) dysarthria neuropathology; (2) the instructions provided to elicit a clear speaking style; (3) the amount of effort exerted by the speaker; and (4) the choice of measures for evaluating efficacy. Finally, we will offer suggestions for future research that may accelerate translation of clear speech research to clinical practice.

Clear speech and phonological typology: A case study of Tashlhiyt Berber

Clear speech is a type of listener-oriented, intelligibility-enhancing mode of speaking. It has been shown to enhance the perceptibility of many different types of phonological contrasts, cross-linguistically. An open question is whether all phonological contrasts are enhanced to an equivalent extent in clear speech. In the current study, we ask whether rarer phonological patterns receive less of a clear speech intelligibility boost, relative to more common phoneme contrasts. Tashlhiyt Berber is an Afroasiatic language spoken in Morocco. Tashlhiyt has been well studied for having typologically uncommon phonotactic properties. This study examines the effect of clear speech on the discrimination of rarer lexical contrasts in Tashlhiyt Berber. We predict that the more typologically uncommon contrasts (e.g., word pairs containing complex and geminate initial onsets) will have a smaller increase in perceptibility from casual to clear speech than more common contrasts (e.g., singleton contrasts). Furthermore, native and naive listeners’ (here, American English speakers) discrimination of these contrasts across speech styles is also compared. Cross-language perception of clear speech provides a window to understanding the phonetic bases for cross-linguistic typological patterns.

Audio-visual clear speech: Articulation, acoustics and perception of segments and tones

Research has established that clear speech with enhanced acoustic signal benefits segmental intelligibility. Less attention has been paid to visible articulatory correlates of clear-speech modifications, or to clear-speech effects at the suprasegmental level (e.g., lexical tone). Questions thus arise as to the extent to which clear-speech cues are beneficial in different input modalities and linguistic domains, and how different resources are incorporated. These questions address the fundamental argument in clear-speech research with respect to the trade-off between effects of signal-based phoneme-extrinsic modifications to strengthen overall acoustic salience versus code-based phoneme-specific modifications to maintain phonemic distinctions. In this talk, we report findings from our studies on audio-visual clear speech production and perception, including vowels and fricatives differing in auditory and visual saliency, and lexical tones believed to lack visual distinctiveness. In a 3-stream study, we use computer-vision techniques to extract visible facial cues associated with segmental and tonal productions in plain and clear speech, characterize distinctive acoustic features across speech styles, and compare audio-visual plain and clear speech perception. Findings are discussed in terms of how speakers and perceivers strike a balance between utilizing general saliency-enhancing and category-specific cues across audio-visual modalities and speech styles with the aim of improving intelligibility.

The clear speech intelligibility benefit for text-to-speech voices: Effects of speaking style and visual guise

This study examined how speaking style and guise influence the intelligibility of text-to-speech (TTS) and naturally produced human voices. Results showed that TTS voices were less intelligible overall. Although using a clear speech style improved intelligibility for both human and TTS voices (using "newscaster" neural TTS), the clear speech effect was stronger for TTS voices. Finally, a visual device guise decreased intelligibility, regardless of voice type. The results suggest that both speaking style and visual guise affect intelligibility of human and TTS voices. Findings are discussed in terms of theories about the role of social information in speech perception.

The relationship between perceived speech clarity and dysphonia: Preliminary investigation

Perceived listener ratings of sentence “clarity” have been used in studies involving clear speech and have been shown to demonstrate a strong correlation with vowel intelligibility as well as a robust clear speech effect (Ferguson and Kerr, 2009; Ferguson and Morgan, 2018). However, it remains unclear what aspects of the speech signal listeners are using to form their perception of speech clarity. It is possible that disruptions in the voice source (i.e., poor voice quality) affect listeners’ perception of clarity. Given the increased prevalence of dysphonia in elderly adults (a target population for clear speech), it is important to determine whether voice quality negatively affects perceptions of speech clarity. The current study aims to examine the relationship between perceived sentence clarity and acoustic and perceptual measures of voice quality. Eighty sentences produced by 10 female talkers (5 healthy young adults and 5 older adults with hearing loss) already rated for perceived clarity by young adult listeners will be analyzed in terms of acoustic measures of voice quality (CPPS, HNR, percent glottal fry, and spectral slope) and perceptual measures of voice quality (CAPE-V evaluation performed by two speech-language pathologists with training in voice disorders).

Influence of clear speech on F0 patterns of Mandarin lexical tones

When communication becomes difficult, a talker may take on a form of communication known as clear speech (Keerstock & Smilijanic, 2019; Picheny et al., 1985). Little is known, however, about clear-speech modifications in tone languages (Zeng, 2017). This study showed how native Mandarin speakers modulate F 0 in tone words through increased variation, raised F 0 onset and offset. Participants read twenty-four sentences varied in four target tones, three times. Sentences were presented in two blocks: casual speech condition (as if talking to friends) and clear speech condition (as if communicating to someone with hearing loss). Data analysis of seven speakers suggested that effects of clear speech on F 0 contours were tone-dependent. As compared with casual speech, in clear speech, F 0 contours of high level (T1), mid-rising (T2), and high-falling (T4) tones were higher within the same tonal context; in contrast, F 0 contours of the low-dipping tone (T3) were lower preceding T1 and T4. F 0 range, onset F 0, and offset F 0 were greater in clear speech mode across most tonal environments. Additional data of eleven speakers has been collected to examine preliminary results and discuss findings in terms of signal-enhancement in clear speech production of lexical tones.

The Effect of Clear Speech on Cantonese Alaryngeal Speakers’ Intelligibility

Background/Aim: The purpose of this study was to provide preliminary data concerning the effect of clear speech (CS) on Cantonese alaryngeal speakers’ intelligibility. Methods: Voice recordings of 11 sentences randomly selected from the Cantonese Sentence Intelligibility Test (CSIT) were obtained from 31 alaryngeal speakers (9 electrolarynx [EL] users, 10 esophageal speakers and 12 tracheoesophageal [TE] speakers) in habitual speech (HS) and CS. Two naïve listeners orthographically transcribed a total of 1,364 sentences. Results: Significant effects of speaking condition on speaking rate and CSIT scores were observed, but no significant effect of alaryngeal communication methods was noted. CS was significantly slower than HS by 0.78 syllables/s. Esophageal speakers demonstrated the slowest speech rate when using CS, while EL users demonstrated the largest decrease in speaking rate when using CS compared to HS. TE speakers had the highest CSIT scores in HS (listener 1 = 81.4%; listener 2 = 81.3%), and esophageal speakers had the highest CSIT scores in CS (listener 1 = 87.5%; listener 2 = 89.7%). EL users experienced the largest increase in intelligibility while using CS compared to HS (9.1%) followed by esophageal speakers (8.9%) and TE speakers (1.4%). Conclusion: Preliminary data indicate that CS may significantly affect Cantonese alaryngeal speakers’ speaking rate and intelligibility. However, intelligibility appeared to vary considerably across speakers. Further research involving larger, heterogeneous groups of speakers and listeners alongside longer and more refined CS training protocols should be conducted to confirm that CS can improve Cantonese alaryngeal speakers’ intelligibility.

The Effects of Clear Speech on American English Listener Perception of Spanish-Accented and Native English Speech

Purpose The purpose of this study was to explore (a) the effect of clear speech on intelligibility, ease of understanding, and accentedness in Spanish-accented and native English speakers of American English and (b) the extent to which accentedness predicts intelligibility and ease of understanding. Method Ten adult talkers, five native English speakers and five native Spanish speakers, read aloud 28 short sentences in habitual speech and clear speech. One hundred monolingual English listeners transcribed what they heard and rated ease of understanding using a 10-cm visual analog scale while hearing the sentences in six-talker babble. Then, accentedness (using a visual analog scale) was judged in quiet. Intelligibility was calculated as the number of words transcribed correctly for each sentence. Ten listeners with significant exposure to Spanish-accented speech rated each talker. Each listener heard only one talker, rating half the sentences in clear speech and half in habitual speech, so that no listener heard a sentence more than once for the intelligibility and ease of understanding assessments. Results Clear speech improved intelligibility and ease of understanding for both language groups, with greater improvement in nonnative talkers. Clear speech did not alter accentedness in nonnative talkers but did increase accentedness in native talkers. Accentedness did not strongly predict intelligibility but did predict ease of understanding, although the relationship was nonlinear. Conclusions Listeners who are experienced in hearing Spanish-accented speech derive significant benefits from clear speech. The difference in the predictability of accentedness for intelligibility and ease of understanding contributes further evidence to the difference in underlying cognitive processes for these two variables.

Tongue- and Jaw-Specific Articulatory Changes and Their Acoustic Consequences in Talkers With Dysarthria due to Amyotrophic Lateral Sclerosis: Effects of Loud, Clear, and Slow Speech.

Purpose This study aimed to determine how tongue and jaw displacement changes impact acoustic vowel contrast in talkers with amyotrophic lateral sclerosis (ALS) and controls. Method Ten talkers with ALS and 14 controls participated in this study. Loud, clear, and slow speech cues were used to elicit tongue and jaw kinematic as well as acoustic changes. Speech kinematics was recorded using three-dimensional articulography. Independent tongue and jaw displacements were extracted during the diphthong /ai/ in kite. Acoustic distance between diphthong onset and offset in Formant 1-Formant 2 vowel space indexed acoustic vowel contrast. Results In both groups, all three speech modifications elicited increases in jaw displacement (typical < slow < loud < clear). By contrast, only slow speech elicited significantly increased independent tongue displacement in the ALS group (typical = loud = clear < slow), whereas all three speech modifications elicited significantly increased independent tongue displacement in controls (typical < loud < clear = slow). Furthermore, acoustic vowel contrast significantly increased in response to clear and slow speech in the ALS group, whereas all three speech modifications elicited significant increases in acoustic vowel contrast in controls (typical < loud < slow < clear). Finally, only jaw displacements accounted for acoustic vowel contrast gains in the ALS group. In controls, however, independent tongue displacements accounted for increases in vowel acoustic contrast during loud and slow speech, whereas jaw and independent tongue displacements accounted equally for acoustic vowel contrast change during clear speech. Conclusion Kinematic findings suggest that slow speech may be better suited to target independent tongue displacements in talkers with ALS than clear and loud speech. However, given that gains in acoustic vowel contrast were comparable for slow and clear speech cues in these talkers, future research is needed to determine potential differential impacts of slow and clear speech on perceptual measures, such as intelligibility. Finally, findings suggest that acoustic vowel contrast gains are predominantly jaw driven in talkers with ALS. Therefore, the acoustic and perceptual consequences of direct instructions of enhanced jaw movements should be compared to cued speech modification, such as clear and slow speech in these talkers.

Cross-linguistic perception of clearly spoken English tense and lax vowels based on auditory, visual, and auditory-visual information

The effect of clear speech on the integration of auditory and visual cues to the tense-lax vowel distinction in English was investigated in native and non-native (Mandarin) perceivers. Clear speech benefits for tense vowels /i, ɑ, u/ were found for both groups across modalities, while lax vowels /ɪ, ʌ, ʊ/ showed a clear speech disadvantage for both groups when presented in the visual-only modality, with Mandarin perceivers showing a further disadvantage for lax vowels presented audio-visually, and no difference in speech styles auditorily. English perceiver responses were then simulated in an ideal perceiver model which both identified auditory (F1, F2, spectral change, duration) and visual (horizontal lip stretch, duration) cues predictive of the clear speech advantage for tense vowels, and indicated which dimensions presented the greatest conflict between cues to tensity and modifications from clear speech (F2 and duration acoustically, duration visually). Altogether, by combining clear speech acoustics, articulation, and perception into a single integrated framework we are able to identify some of the signal properties responsible for both beneficial and detrimental speech style modifications.

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.

Clear speech improves listeners' recall.

The present study examined the effect of intelligibility-enhancing clear speech on listeners' recall. Native (n = 57) and non-native (n = 31) English listeners heard meaningful sentences produced in clear and conversational speech, and then completed a cued-recall task. Results showed that listeners recalled more words from clearly produced sentences. Sentence-level analysis revealed that listening to clear speech increased the odds of recalling whole sentences and decreased the odds of erroneous and omitted responses. This study showed that the clear speech benefit extends beyond word- and sentence-level recognition memory to include deeper linguistic encoding at the level of syntactic and semantic information.

The effect of clear speech and masking noise on listening effort in native and non-native listeners

Listening effort increases when perceiving speech masked by noise and when listeners are non-native speakers of the target language (Zekveld and Kramer, 2014; Borghini and Hazan, 2018). Listener-oriented clear speech (CS) improves word recognition in noise and recognition memory (Keerstock and Smiljanic, 2018). It is unclear, however, whether the CS benefit can be explained by reduced listening effort during processing of easier-to-understand speech. The goal of this study was to examine the effect of CS on listening effort associated with degraded listening conditions differing in the source of difficulty and underlying cognitive mechanism: energetic masking, informational masking, and non-native listening. Native and non-native English listeners performed a word recognition in noise task and a visual response task, i.e., pressing keys to indicate the orientation of an arrow on the screen, first separately and then simultaneously. In the word recognition task, listeners repeated back sentences produced in CS and conversational speech and mixed with speech-shaped noise and 2-talker babble. The presentation will discuss analyses aimed at uncovering how hyper-articulated CS and masker type influence listening effort for native and non-native listeners as measured by objective and subjective dual-task cost.

Speaking clearly improves speech segmentation in optimal listening conditions

Speaking clearly improves intelligibility particularly in noisy environments—a benefit that may be partly attributed to enhanced ease of speech segmentation. However, speech segmentation is facilitated by coarticulation (Fernandes et al., 2007), which may be reduced in hyper-articulated clear speech (Scarborough and Zellou, 2013). This study investigated the effect of clear speech on speech segmentation in quiet and in noise for native and non-native listeners with an artificial language (AL) learning experiment. Six trisyllabic AL words (e.g., /kutupi/) were produced by a native English speaker both clearly and conversationally. Six speech streams were created, each containing 20 pitch-flattened tokens of each AL word concatenated in random order without intervening pauses. In the learning phase, participants heard either conversational or clear AL speech streams in quiet or masked with speech-shaped noise. Next, in a two-alternative forced-choice test, participants identified the AL words spoken in quiet and in the style they were exposed to. Preliminary results showed that clear speech improved segmentation relative to conversational speech for native English listeners in quiet only. The results suggest that the use of exaggerated information about segment identity aids speech segmentation in optimal listening conditions but is disrupted under perceptual load.

Effect of Clear Speech on the Duration of Silent Intervals at Syntactic and Phonemic Boundaries in the Speech of Individuals With Parkinson Disease.

Purpose The purpose of the current investigation was to determine the extent to which individuals with and without Parkinson disease (PD) modified silent interval durations when using a clear speaking style. Method Ten individuals with idiopathic PD and 10 older adult control speakers produced a reading passage using both habitual and clear speaking styles. Silent intervals lasting 15 ms and longer were identified and extracted. Each silent interval was categorized according to the surrounding syntactic context of the reading passage. In addition, voiceless stop gaps that occurred within words, phrases, or clauses were categorized by the preceding phonemic context. Results Statistical analyses revealed that all participants increased silent interval duration with a clear speaking style at inter-sentence and intra-sentence syntactic boundaries. Compared to controls, individuals with PD exhibited significantly less increase in silent interval durations at these syntactic boundaries. Control speakers also increased silent stop gap durations in the clear speaking style regardless of preceding phonemic context. Individuals with PD, however, only increased stop gap duration when the silent interval was preceded by a sonorant. Conclusion These findings suggest that speakers with PD exhibit less clarity-related increase in silent interval duration than control speakers. In addition, speakers with PD exhibited significant increases in silent interval duration that coincided with syntactic boundaries of the reading passage but little to no clarity-related modulation of stop gap intervals. Therefore, these data suggest that speakers with PD exhibited changes in silent interval durations that were more so associated with modulation of speech prosody than articulation when using a clearer speaking style.