Development and evaluation of methods for assessing tone production skills in Mandarin-speaking children with cochlear implants

High variability phonetic training facilitates perception-to-production transfer in Mandarin-speaking children with cochlear implants: An acoustic investigation

This study primarily aimed to evaluate the effectiveness of high variability phonetic training (HVPT) for children with cochlear implants (CIs) via the cross-modal transfer of perceptual learning to lexical tone production, a scope that has been largely neglected by previous training research. Sixteen CI participants received a five-session HVPT within a period of three weeks, whereas another 16 CI children were recruited without receiving any formal training. Lexical tone production was assessed with a picture naming task before the provision (pretest) and immediately after (posttest) and ten weeks after (follow-up test) the completion of the training protocol. The production samples were coded and analyzed acoustically. Despite considerable distinctions from the typical baselines of normal-hearing peers, the trained CI children exhibited significant improvements in Mandarin tone production from pretest to posttest in pitch height of T1, pitch slope of T2, and pitch curvature of T3. Moreover, the training-induced acoustic changes in the concave characteristic of the T3 contour was retained ten weeks after training termination. This study represents an initial acoustic investigation on HVPT-induced benefits in lexical tone production for the pediatric CI population, which provides valuable insights into applying this perceptual training technique as a viable tool in clinical practices.

Mandarin-speaking Children With Cochlear Implants Face Challenges in Using F0 Expansion to Express Contrastive Focus

OBJECTIVES

Children with cochlear implants (CIs) face challenges in perceiving fundamental frequency (F0) information because CIs do not transmit F0 effectively. In Mandarin, F0 can contrast meanings at the word level, that is, via lexical tones with distinct F0 contours, and signal contrastive relations between words at the utterance-level, that is, via contrastive focus with expanded F0 range and longer duration. Mandarin-speaking children with CIs have been reported to face challenges in producing distinct F0 contours across tones, but early implantation facilitates tonal acquisition. However, it is still unclear if utterance-level prosody, such as contrastive focus, is also challenging for these children, and if early implantation also offers benefits for focus production. Therefore, this study asked how accurately children with CIs can produce contrastive focus, and if early implantation leads to more accurate focus production, with acoustic patterns approaching that of children with typical hearing (TH).

DESIGN

Participants included 55 Mandarin-speaking children (3 to 7 years) with CIs and 55 age-matched children with TH. Children produced noun phrases with and without contrastive focus, such as RED-COLORED cat versus red-colored cat . Three adult native listeners perceptually scored the productions as correct or incorrect. The "correct" productions were then acoustically analyzed in terms of F0 range and duration.

RESULTS

Based on the perceptual scores, children with CIs produced focus with significantly lower accuracy (38%) than their TH peers (84%). The acoustic analysis on their "correct" productions showed that children with TH used both F0 and duration to mark focus, producing focal syllables with an expanded F0 range and long duration, and postfocal syllables with a reduced F0 range and short duration. However, children with CIs differed from children with TH in that they produced focal syllables with long duration but not an expanded F0 range, although they produced postfocal syllables with a reduced F0 range and short duration like their TH peers. In addition, early implantation correlated with the percept of more accurate focus productions and better use of F0 range in focal marking.

CONCLUSIONS

This study finds that Mandarin-speaking children with CIs are still learning to apply appropriate acoustic cues to contrastive focus. The challenge appears to lie in the use of an expanded F0 range to mark focus, probably related to the limited transmission of F0 information through the CI devices. These findings thus have implications for parents and those working with children with CIs, showing that utterance-level prosody also requires speech remediation, and underscores the critical role of identifying problems early in the acquisition of F0 functions in Mandarin, not only at the word level but also at the utterance-level.

Investigating Perception to Production Transfer in Children With Cochlear Implants: A High Variability Phonetic Training Study

PURPOSE

This study builds upon an established effective training method to investigate the advantages of high variability phonetic identification training for enhancing lexical tone perception and production in Mandarin-speaking pediatric cochlear implant (CI) recipients, who typically face ongoing challenges in these areas.

METHOD

Thirty-two Mandarin-speaking children with CIs were quasirandomly assigned into the training group (TG) and the control group (CG). The 16 TG participants received five sessions of high variability phonetic training (HVPT) within a period of 3 weeks. The CG participants did not receive the training. Perception and production of Mandarin tones were administered before (pretest) and immediately after (posttest) the completion of HVPT via lexical tone recognition task and picture naming task. Both groups participated in the identical pretest and posttest with the same time frame between the two test sessions.

RESULTS

TG showed significant improvement from pretest to posttest in identifying Mandarin tones for both trained and untrained speech stimuli. Moreover, perceptual learning of HVPT significantly facilitated trainees' production of T1 and T2 as rated by a cohort of 10 Mandarin-speaking adults with normal hearing, which was corroborated by acoustic analyses revealing improved fundamental frequency (F0) median for T1 and T2 production and enlarged F0 movement for T2 production. In contrast, TG children's production of T3 and T4 showed nonsignificant changes across two test sessions. Meanwhile, CG did not exhibit significant changes in either perception or production.

CONCLUSIONS

The results suggest a limited and inconsistent transfer of perceptual learning to lexical tone production in children with CIs, which challenges the notion of a robust transfer and highlights the complexity of the interaction between perceptual training and production outcomes. Further research on individual differences with a longitudinal design is needed to optimize the training protocol or tailor interventions to better meet the diverse needs of learners.

Production of Tone 2 in disyllabic words in Mandarin Chinese speaking children aged 3-5 with a cochlear implant and a contralateral hearing aid

To investigate Mandarin Tone 2 production of disyllabic words of prelingually deafened children with a cochlear implant (CI) and a contralateral hearing aid (HA) and to evaluate the relationship between their demographic variables and tone-production ability. Thirty prelingually Mandarin-speaking preschoolers with CI+HA and 30 age-matched normal-hearing (NH) children participated in the study. Fourteen disyllabic words were recorded from each child. A total of 840 tokens (14 × 60) were then used in tone-perception tests in which four speech therapists participated. The production of T2-related disyllabic words of the bimodal group was significantly worse than that of the NH group, as reflected in the overall accuracy (88.57% ± 16.31% vs 99.29% ± 21.79%, p < 0.05), the accuracy of T1+T2 (93.33% vs 100%), the accuracy of T2+T1 (66.67 ± 37.91% vs 98.33 ± 9.13%), and the accuracy of T2+T4 (78.33 ± 33.95% vs 100%). In addition, the bimodal group showed significantly inferior production accuracy of T2+T1 than T2+T2 and T3+T2, p < 0.05. Both bimodal age and implantation age were significantly negatively correlated with the overall production accuracy, p < 0.05. For the error patterns, bimodal participants experienced more errors when T2 was in the first position of the tone combination, and T2 was most likely to be mispronounced as T1 and T3. Bimodal patients aged 3-5 have T2-related disyllabic lexical tone production defects, and their performances are related to tone combination, implantation age, and bimodal age.

Intelligibility of Word-Initial Obstruent Consonants in Mandarin-Speaking Prelingually Deafened Children With Cochlear Implants

PURPOSE

This study assessed the intelligibility of obstruent consonants in prelingually deafened Mandarin-speaking children with cochlear implants (CIs).

METHOD

Twenty-two Mandarin-speaking children with normal hearing (NH) aged 3.25-10.0 years and 35 Mandarin-speaking children with CIs aged 3.77-15.0 years were recruited to produce a list of Mandarin words composed of 17 word-initial obstruent consonants in different vowel contexts. The children with CIs were assigned to chronological age-matched (CA) and hearing age-matched (HA) subgroups with reference to the NH controls. One hundred naïve NH adult listeners were recruited for a consonant identification task that consisted of a total of 2,663 stimulus tokens through an online research platform. For each child speaker, the consonant productions were judged by seven to 12 different adult listeners. An average percentage of consonants correct was calculated across all listeners for each consonant.

RESULTS

The CI children in both the CA and HA subgroups showed lower intelligibility in their consonant productions than the NH controls. Among the 17 obstruents, both CI subgroups showed higher intelligibility for stops, but they demonstrated major problems with the sibilant fricatives and affricates and showed a different confusion pattern from the NH controls on these sibilants. Of the three places (alveolar, alveolopalatal, and retroflex) in Mandarin sibilants, both CI subgroups showed the lowest intelligibility and the greatest difficulties with alveolar sounds. For the NH children, there was a significant positive relationship between overall consonant intelligibility and chronological age. For the children with CIs, the best fit regression model revealed significant effects of chronological age and age at implantation, with their quadratic terms included.

CONCLUSIONS

Mandarin-speaking children with CIs experience major challenges in the three-way place contrasts of sibilant sounds in consonant production. Chronological age and the combined effect of CI-related time variables play important roles in the development of obstruent consonants in the CI children.

Acoustic analysis of tone production in Mandarin-speaking bimodal cochlear implant users

The benefit of using a hearing aid with a cochlear implant (bimodal hearing) has been demonstrated for tone perception under certain conditions. The present study evaluated bimodal effects for tone production by comparing performance between a bimodal and a unimodal implant group. Results showed that acoustic differentiation of tones produced by the bimodal group was better than the unimodal implant group, and performance was dependent on the subject's acoustic thresholds but not related to implant experience or age at implantation. The findings support the use of amplified acoustic hearing in conjunction with the implant for better development of pitch production.

Speech production in Mandarin-speaking children with cochlear implants: a systematic review

OBJECTIVE

This study aimed to systematically review and critically appraise the literature describing the phonetic characteristics and accuracy of the consonants, vowels and tones produced by Mandarin-speaking children with cochlear implants (CIs).

DESIGN

The protocol in this review was designed in conformity with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. EBSCOhost, PubMed, Scopus, PsycINFO, ProQuest Central databases were searched for relevant articles which met the inclusion criteria.

STUDY SAMPLE

A total of 18 journal papers were included in this review.

RESULTS

The results revealed that Mandarin-speaking children with CIs perform consistently more poorly in their production of consonants, in particular on fricatives, have a smaller and less well-defined vowel space, and exhibit greater difficulties in tone realisation, notably T2 and T3, when compared to their normal-hearing (NH) peers. The results from acoustic and accuracy analyses are negatively correlated with CI implantation age, but largely positively correlated with hearing age.

CONCLUSIONS

Findings of this review highlight the factors that influence consonant, vowel and tone production in Mandarin-speaking children with CIs, thereby providing critical information for clinicians and researchers working with this population.

Dialect Effects on Mandarin Tone Perception Development

This study aimed to characterize factors that influence early dialect development in a language environment with multiple dialects. Children were evaluated for these dialect effects compared with normal hearing referenced measures of speech and language development that are commonly implemented in hearing-impaired children. Dialect exposure and use were assessed longitudinally in Chinese children (2-6 years old) that were raised in a community where Putonghua (PTH) and Sichuanhua (SCH) Mandarin dialects were used. Lexical tones in these dialects are different. A total of 20 boys and 20 girls (2 years old at the beginning of the study) that attended the same nursery school were included in this study. SCH was used by the majority of subjects <4 years old. The majority of subjects >4 years old used either dialect, with a few users of both dialects at this age. PTH tone perception did not differ significantly as a function of dialect use. Tone recognition and discrimination were >90% accurate by 6 years old, in contrast to previous results for children with minimal exposure and use of PTH. Children with approximately ⩾50% PTH exposure might be accurately assessed with norm-referenced speech materials spoken in PTH, regardless of their preferred dialect. However, the current norm-referenced assessments of children with minimal PTH exposure and nonusers of the dialect might be inaccurate.

Acoustic Assessment of Tone Production of Prelingually-Deafened Mandarin-Speaking Children With Cochlear Implants

Objective

The purpose of the present study was to investigate Mandarin tone production performance of prelingually deafened children with cochlear implants (CIs) using modified acoustic analyses and to evaluate the relationship between demographic factors of those CI children and their tone production ability.

Methods

Two hundred seventy-eight prelingually deafened children with CIs and 173 age-matched normal-hearing (NH) children participated in the study. Thirty-six monosyllabic Mandarin Chinese words were recorded from each subject. The fundamental frequencies (F0) were extracted from the tone tokens. Two acoustic measures (i.e., differentiability and hit rate) were computed based on the F0 onset and offset values (i.e., the tone ellipses of the two-dimensional [2D] method) or the F0 onset, midpoint, and offset values (i.e., the tone ellipsoids of the 3D method). The correlations between the acoustic measures as well as between the methods were performed. The relationship between demographic factors and acoustic measures were also explored.

Results

The children with CIs showed significantly poorer performance in tone differentiability and hit rate than the NH children. For both CI and NH groups, performance on the two acoustic measures was highly correlated with each other (r values: 0.895–0.961). The performance between the two methods (i.e., 2D and 3D methods) was also highly correlated (r values: 0.774–0.914). Age at implantation and duration of CI use showed a weak correlation with the scores of acoustic measures under both methods. These two factors jointly accounted for 15.4–18.9% of the total variance of tone production performance.

Conclusion

There were significant deficits in tone production ability in most prelingually deafened children with CIs, even after prolonged use of the devices. The strong correlation between the two methods suggested that the simpler, 2D method seemed to be efficient in acoustic assessment for lexical tones in hearing-impaired children. Age at implantation and especially the duration of CI use were significant, although weak, predictors for tone development in pediatric CI users. Although a large part of tone production ability could not be attributed to these two factors, the results still encourage early implantation and continual CI use for better lexical tone development in Mandarin-speaking pediatric CI users.

Discrimination and identification of lexical tones and consonants in Mandarin-speaking children using cochlear implants

Mandarin-speaking adults using cochlear implants (CI) experience more difficulties in perceiving lexical tones than consonants. This problem may result from the fact that CIs provide relatively sufficient temporal envelope information for consonant perception in quiet environments, but do not convey the fine spectro-temporal information considered to be necessary for accurate pitch perception. Another possibility is that Mandarin speakers with post-lingual hearing loss have developed language-specific use of these acoustic cues, impeding lexical tone processing under CI conditions. To investigate this latter hypothesis, syllable discrimination and word identification abilities for Mandarin consonants (place and manner) and lexical-tone contrasts (tones 1 vs 3 and 1 vs 2) were measured in 15 Mandarin-speaking children using CIs and age-matched children with normal hearing (NH). In the discrimination task, only children using CIs exhibited significantly lower scores for consonant place contrasts compared to other contrasts, including lexical tones. In the word identification task, children using CIs showed lower performance for all contrasts compared to children with NH, but they both showed specific difficulties with tone 1 vs 2 contrasts. This study suggests that Mandarin-speaking children using CIs are able to discriminate and identify lexical tones and, perhaps more surprisingly, have more difficulties when discriminating consonants.

Processing of Acoustic Information in Lexical Tone Production and Perception by Pediatric Cochlear Implant Recipients

Purpose: This study examined the utilization of multiple types of acoustic information in lexical tone production and perception by pediatric cochlear implant (CI) recipients who are native speakers of Mandarin Chinese. Methods: Lexical tones were recorded from CI recipients and their peers with normal hearing (NH). Each participant was asked to produce a disyllabic word, yan jing, with which the first syllable was pronounced as Tone 3 (a low dipping tone) while the second syllable was pronounced as Tone 1 (a high level tone, meaning "eyes") or as Tone 4 (a high falling tone, meaning "eyeglasses"). In addition, a parametric manipulation in fundamental frequency (F0) and duration of Tones 1 and 4 used in a lexical tone recognition task in Peng et al. (2017) was adopted to evaluate the perceptual reliance on each dimension. Results: Mixed-effect analyses of duration, intensity, and F0 cues revealed that NH children focused exclusively on marking distinct F0 contours, while CI participants shortened Tone 4 or prolonged Tone 1 to enhance their contrast. In line with these production strategies, NH children relied primarily on F0 cues to identify the two tones, whereas CI children showed greater reliance on duration cues. Moreover, CI participants who placed greater perceptual weight on duration cues also tended to exhibit smaller changes in their F0 production. Conclusion: Pediatric CI recipients appear to contrast the secondary acoustic dimension (duration) in addition to F0 contours for both lexical tone production and perception. These findings suggest that perception and production strategies of lexical tones are well coupled in this pediatric CI population.

Bilaterally Combined Electric and Acoustic Hearing in Mandarin-Speaking Listeners: The Population With Poor Residual Hearing

The hearing loss criterion for cochlear implant candidacy in mainland China is extremely stringent (bilateral severe to profound hearing loss), resulting in few patients with substantial residual hearing in the nonimplanted ear. The main objective of the current study was to examine the benefit of bimodal hearing in typical Mandarin-speaking implant users who have poorer residual hearing in the nonimplanted ear relative to those used in the English-speaking studies. Seventeen Mandarin-speaking bimodal users with pure-tone averages of ∼80 dB HL participated in the study. Sentence recognition in quiet and in noise as well as tone and word recognition in quiet were measured in monaural and bilateral conditions. There was no significant bimodal effect for word and sentence recognition in quiet. Small bimodal effects were observed for sentence recognition in noise (6%) and tone recognition (4%). The magnitude of both effects was correlated with unaided thresholds at frequencies near voice fundamental frequencies (F0s). A weak correlation between the bimodal effect for word recognition and unaided thresholds at frequencies higher than F0s was identified. These results were consistent with previous findings that showed more robust bimodal benefits for speech recognition tasks that require higher spectral resolution than speech recognition in quiet. The significant but small F0-related bimodal benefit was also consistent with the limited acoustic hearing in the nonimplanted ear of the current subject sample, who are representative of the bimodal users in mainland China. These results advocate for a more relaxed implant candidacy criterion to be used in mainland China.

Vocal Biomarkers of Mild-to-Moderate Hearing Loss in Children and Adults: Voiceless Sibilants

PURPOSE

The purpose of this study was to determine if an objective measure of speech production could serve as a vocal biomarker for the effects of high-frequency hearing loss on speech perception. It was hypothesized that production of voiceless sibilants is governed sufficiently by auditory feedback that high-frequency hearing loss results in subtle but significant shifts in the spectral characteristics of these sibilants.

METHOD

Sibilant production was examined in individuals with mild to moderately severe congenital (22 children; 8-17 years old) and acquired (23 adults; 55-80 years old) hearing losses. Measures of hearing level (pure-tone average thresholds at 4 and 8 kHz), speech perception (detection of nonsense words within sentences), and speech production (spectral center of gravity [COG] for /s/ and /ʃ/) were obtained in unaided and aided conditions.

RESULTS

For both children and adults, detection of nonsense words increased significantly as hearing thresholds improved. Spectral COG for /ʃ/ was unaffected by hearing loss in both listening conditions, whereas the spectral COG for /s/ significantly decreased as high-frequency hearing loss increased. The distance in spectral COG between /s/ and /ʃ/ decreased significantly with increasing hearing level. COG distance significantly predicted nonsense-word detection in children but not in adults.

CONCLUSIONS

At least one aspect of speech production (voiceless sibilants) is measurably affected by high-frequency hearing loss and is related to speech perception in children. Speech production did not predict speech perception in adults, suggesting a more complex relationship between auditory feedback and feedforward mechanisms with age. Even so, these results suggest that this vocal biomarker may be useful for identifying the presence of high-frequency hearing loss in adults and children and for predicting the impact of hearing loss in children.

Pulse-rate discrimination deficit in cochlear implant users: is the upper limit of pitch peripheral or central?

Cochlear implant (CI) users do not reliably associate an increase in pulse rate above 300 pulses per second (pps) with an increase in pitch. The locus of this upper limit of pitch remains unknown. The present study tested the hypothesis that this deficit resides at least initially at the auditory nerve. The hypothesis was tested by comparing pulse rate discrimination in different neural excitation patterns, in which a large versus small population of auditory nerve fibers was activated. If poorer pulse rate discrimination was found under conditions where narrower spread of neural excitation (SOE) was anticipated where a relatively small neural population was activated, then it would support the hypothesis that the rate processing deficit found in CI users is related to peripheral neural degeneration. Nine listeners (12 ears) implanted with the Cochlear Americas Nucleus^® devices participated in the study. Different SOE conditions were created by (1) selecting electrodes that showed narrow versus broad forward-masked psychophysical spatial tuning curves, and (2) by measuring these electrodes in monopolar (MP) and narrow bipolar (BP0) electrode configurations. Rate discrimination difference limen (DL) was measured at the selected electrodes in two electrode configurations at three base rates (200, 300 and 500 pps). Consistent with the prediction, group mean DL was better (1) at stimulation sites measured with broader tuning, and (2) in MP relative to BP stimulation. These effects were more salient at the more challenging base rates. There was a weak relationship between rate discrimination (above thresholds) and the effect of rate on detection thresholds. Finally, rate discrimination at rates above the known upper limit (i.e., 500 pps) was correlated with duration of deafness and highly predicted the subjects' speech recognition performance in noise. These findings support that pulse rate discrimination depends, at least partially, on neural conditions at the auditory periphery and this peripheral limit predicts speech recognition outcomes with a CI.

Adaptation in Mandarin tone production with pitch-shifted auditory feedback: Influence of tonal contrast requirements

We investigated Mandarin speakers' control of lexical tone production with F0-perturbed auditory feedback. Subjects produced high level (T1), mid rising (T2), low dipping (T3), and high falling (T4) tones in conditions with (a) no perturbation, (b) T1 shifted down, (c) T1 shifted down and T3 shifted up, or (d) T1 shifted down and T3 shifted up but without producing other tones. Speakers and new subjects also completed a tone identification task with unaltered and F0-perturbed productions. With only T1 perturbed down, speakers adapted by raising F0 relative to no-perturbation. With simultaneous T1 down and T3 up perturbations, no T1 adaptation occurred, and T3 adaptation occurred only if T2 was also produced. Identification accuracy with stimuli representing adapted productions was comparable to baseline, but with simulated non-adapted productions it was reduced for T2 and T3. Thus, Mandarin speakers' adaptation to F0 perturbations is linguistically constrained and serves to maintain tone contrast.

The effectiveness of sound-processing strategies on tonal language cochlear implant users: A systematic review

IMPORTANCE

Contemporary cochlear implants (CIs) are well established as a technology for people with severe-to-profound sensorineural hearing loss, with their effectiveness having been widely reported. However, for tonal language CI recipients, speech perception remains a challenge: Conventional signal processing strategies have been demonstrated to possibly provide insufficient information to encode tonal cues, and CI recipients have exhibited considerable deficits in tone perception. Thus, some tonal language-oriented sound-processing strategies have been introduced. The effects of available tonal language-oriented strategies on tone perception are reviewed and evaluated in this study. The results may aid in designing and improving tonal language-appropriate sound-processing strategies for CI recipients.

OBJECTIVE

The objective of this systematic review was to investigate the effects of tonal-language-oriented signal processing strategies on tone perception, music perception, word and sentence recognition.

METHODS

To evaluate the effects of tonal language-oriented strategies on tone perception, we conducted a systematic review. We searched for relevant reports dated from January 1979 to July 2017 using PubMed, Cochrane Library, EBSCO, Web of Science, EMBASE, and 4 Chinese periodical databases (CBMdisc, CNKI, VIP, and Wanfang Data).

RESULTS

According to our search strategy, 672 potentially eligible studies were retrieved from the databases, with 12 of these studies included in the final review after a 4-stage selection process. The majority of sound-processing strategies designed for tonal language were HiResolution® with Fidelity 120 (HiRes 120), fine structure processing, temporal fine structure (TFS), and C-tone. Generally, acute or short-term comparisons between the tonal language-oriented strategies and the conventional strategy did not reveal statistically significant differences in speech perception (or show a small improvement). However, a tendency toward improved tone perception and subjectively reported overall preferred sound quality was observed with the tonal language-oriented strategies.

INTERPRETATION

Conventional signal processing strategies typically provided very limited F0 information via temporal envelopes delivered to the stimulating electrodes. In contrast, tonal language-oriented coding strategies attempted to present more spectral information and TFS cues required for tone perception. Thus, a tendency of improved performance in tonal language perception in CI users was shown.

Mandarin compound vowels produced by prelingually deafened children with cochlear implants

OBJECTIVE

Compound vowels including diphthongs and triphthongs have complex, dynamic spectral features. The production of compound vowels by children with cochlear implants (CIs) has not been studied previously. The present study examined the dynamic features of compound vowels in native Mandarin-speaking children with CIs.

METHODS

Fourteen prelingually deafened children with CIs (aged 2.9-8.3 years old) and 14 age-matched, normal-hearing (NH) children produced monosyllables containing six Mandarin compound vowels (i.e., /aɪ/, /aʊ/, /uo/, /iɛ/, /iaʊ/, /ioʊ/). The frequency values of the first two formants were measured at nine equidistant time points over the course of the vowel duration. All formant frequency values were normalized and then used to calculate vowel trajectory length and overall spectral rate of change.

RESULTS

The results revealed that the CI children produced significantly longer durations for all six compound vowels. The CI children's ability to produce formant movement for the compound vowels varied considerably. Some CI children produced relatively static formant trajectories for certain diphthongs, whereas others produced certain vowels with greater formant movement than did the NH children. As a group, the CI children roughly followed the NH children on the pattern of magnitude of formant movement, but they showed a slower rate of formant change than did the NH children.

CONCLUSIONS

The findings suggested that prelingually deafened children with CIs, during the early stage of speech acquisition, had not established appropriate targets and articulatory coordination for compound vowel productions. This preliminary study may shed light on rehabilitation of prelingually deafened children with CIs.

Mandarin Tone Identification in Cochlear Implant Users Using Exaggerated Pitch Contours

OBJECTIVE

To determine whether exaggerating the variations in fundamental frequency (F0) contours of Mandarin-based pitch fluctuations could improve tone identification by cochlear implant (CI) users.

METHODS

Twelve normal-hearing (NH) listeners and 11 CI users were tested for their ability to recognize F0 contours modeled after Mandarin tones, in 4- or 5-alternatives forced-choice paradigms. Two types of stimuli were used: computer-generated complex tones and voice recordings. Four contours were tested with voice recordings: flat, rise, fall, and dip. A fifth contour, peak, was added for complex tones. The F0 range of each contour was varied in an adaptive manner. A maximum-likelihood technique was used to fit a psychometric function to the performance data and extract threshold at 70% accuracy.

RESULTS

As F0 range increased, performance in tone identification improved but did not reach 100% for some CI users, suggesting that confusions between contours could always be made even with extremely exaggerated contours. Compared with NH participants, CI users required substantially larger F0 ranges to identify tones, on the order of 9.3 versus 0.4 semitones. CI users achieved better performance for complex tones than for voice recordings, whereas the reverse was true for NH participants. Confusion matrices showed that the "flat" tone was often a default option when the tone contour's F0 range presented was too narrow for participants to respond correctly.

CONCLUSION

These results demonstrate markedly impaired ability for CI users to identify tonal contours, but suggest that the use of exaggerated pitch contours may be helpful for tonal language perception.

Lexical tone recognition in noise in normal-hearing children and prelingually deafened children with cochlear implants

OBJECTIVE

The purpose of the present study was to investigate Mandarin tone recognition in background noise in children with cochlear implants (CIs), and to examine the potential factors contributing to their performance.

DESIGN

Tone recognition was tested using a two-alternative forced-choice paradigm in various signal-to-noise ratio (SNR) conditions (i.e. quiet, +12, +6, 0, and -6 dB). Linear correlation analysis was performed to examine possible relationships between the tone-recognition performance of the CI children and the demographic factors.

STUDY SAMPLE

Sixty-six prelingually deafened children with CIs and 52 normal-hearing (NH) children as controls participated in the study.

RESULTS

Children with CIs showed an overall poorer tone-recognition performance and were more susceptible to noise than their NH peers. Tone confusions between Mandarin tone 2 and tone 3 were most prominent in both CI and NH children except for in the poorest SNR conditions. Age at implantation was significantly correlated with tone-recognition performance of the CI children in noise.

CONCLUSIONS

There is a marked deficit in tone recognition in prelingually deafened children with CIs, particularly in noise listening conditions. While factors that contribute to the large individual differences are still elusive, early implantation could be beneficial to tone development in pediatric CI users.

Current trends in outcome studies for children with hearing loss and the need to establish a comprehensive framework of measuring outcomes in children with hearing loss in China

Since the 1970s, outcome studies for children with hearing loss expanded from focusing on assessing auditory awareness and speech perception skills to evaluating language and speech development. Since the early 2000s, the multi-center large scale research systematically studied outcomes in the areas of auditory awareness, speech-perception, language development, speech development, educational achievements, cognitive development, and psychosocial development. These studies advocated the establishment of baseline and regular follow-up evaluations with a comprehensive framework centered on language development. Recent research interests also include understanding the vast differences in outcomes for children with hearing loss, understanding the relationships between neurocognitive development and language acquisition in children with hearing loss, and using outcome studies to guide evidence-based clinical practice. After the establishment of standardized Mandarin language assessments, outcomes research in Mainland China has the potential to expand beyond auditory awareness and speech perception studies.

Acoustic properties of vowel production in prelingually deafened Mandarin-speaking children with cochlear implants

The present study examined the acoustic features of vowel production in Mandarin-speaking children with cochlear implants (CIs). The subjects included 14 native Mandarin-speaking, prelingually deafened children with CIs (2.9-8.3 yr old) and 60 age-matched, normal-hearing (NH) children (3.1-9.0 years old). Each subject produced a list of monosyllables containing seven Mandarin vowels: [i, a, u, y, ɤ, ʅ, ɿ]. Midpoint F1 and F2 of each vowel token were extracted and normalized to eliminate the effects of different vocal tract sizes. Results showed that the CI children produced significantly longer vowels and less compact vowel categories than the NH children did. The CI children's acoustic vowel space was reduced due to a retracted production of the vowel [i]. The vowel space area showed a strong negative correlation with age at implantation (r = -0.80). The analysis of acoustic distance showed that the CI children produced corner vowels [a, u] similarly to the NH children, but other vowels (e.g., [ʅ, ɿ]) differently from the NH children, which suggests that CI children generally follow a similar developmental path of vowel acquisition as NH children. These findings highlight the importance of early implantation and have implications in clinical aural habilitation in young children with CIs.

Acoustic properties of vocal singing in prelingually-deafened children with cochlear implants or hearing aids

OBJECTIVE

The purpose of the present study was to investigate vocal singing performance of hearing-impaired children with cochlear implants (CI) and hearing aids (HA) as well as to evaluate the relationship between demographic factors of those hearing-impaired children and their singing ability.

METHODS

Thirty-seven prelingually-deafened children with CIs and 31 prelingually-deafened children with HAs, and 37 normal-hearing (NH) children participated in the study. The fundamental frequencies (F0) of each note in the recorded songs were extracted and the duration of each sung note was measured. Five metrics were used to evaluate the pitch-related and rhythm-based aspects of singing accuracy.

RESULTS

Children with CIs and HAs showed significantly poorer performance in either the pitch-based assessments or the rhythm-based measure than the NH children. No significant differences were seen between the CI and HA groups in all of these measures except for the mean deviation of the pitch intervals. For both hearing-impaired groups, length of device use was significantly correlated with singing accuracy.

CONCLUSIONS

There is a marked deficit in vocal singing ability either in pitch or rhythm accuracy in a majority of prelingually-deafened children who have received CIs or fitted with HAs. Although an increased length of device use might facilitate singing performance to some extent, the chance for the hearing-impaired children fitted with either HAs or CIs to reach high proficiency in singing is quite slim.

Relationship between tone perception and production in prelingually deafened children with cochlear implants

HYPOTHESIS

Performance in tone perception and production are correlated in prelingually deafened pediatric cochlear implant (CI) users across individuals. Demographic variables, such as age at implantation, contribute to the performance variability.

BACKGROUND

Poor representation of pitch information in CI devices hinders pitch perception and affects perception of lexical tones in cochlear implant users who speak tonal languages.

METHODS

One hundred ten Mandarin-speaking, prelingually deafened CI subjects and 125 typically developing, normal-hearing subjects were recruited from Beijing, China. Lexical tone perception was measured using a computerized tone contrast test. Tone production was judged by native Mandarin-speaking adult listeners as well as analyzed acoustically and with an artificial neural network. A general linear model analysis was performed to determine factors that accounted for performance variability.

RESULTS

CI subjects scored ≈ 67% correct on the lexical tone perception task. The degree of differentiation of tones produced by the CI group was significantly lower than the control group as revealed by acoustic analysis. Tone production performance assessed by the neural network was highly correlated with that evaluated by human listeners. There was a moderate correlation between the overall tone perception and production performance across CI subjects. Duration of implant use and age at implantation jointly explained ≈ 29% of the variance in the tone perception performance. Age at implantation was the only significant predictor for tone production performance in the CI subjects.

CONCLUSION

Tone production performance in pediatric CI users is dependent on accurate perception. Early implantation predicts a better outcome in lexical tone perception and production.

The ear is connected to the brain: some new directions in the study of children with cochlear implants at Indiana University

Since the early 1980s, the DeVault Otologic Research Laboratory at the Indiana University School of Medicine has been on the forefront of research on speech and language outcomes in children with cochlear implants. This paper highlights work over the last decade that has moved beyond collecting speech and language outcome measures to focus more on investigating the underlying cognitive, social, and linguistic skills that predict speech and language outcomes. This recent work reflects our growing appreciation that early auditory deprivation can affect more than hearing and speech perception. The new directions include research on attention to speech, word learning, phonological development, social development, and neurocognitive processes. We have also expanded our subject populations to include infants and children with additional disabilities.

Predicting the intelligibility of vocoded and wideband Mandarin Chinese

Due to the limited number of cochlear implantees speaking Mandarin Chinese, it is extremely difficult to evaluate new speech coding algorithms designed for tonal languages. Access to an intelligibility index that could reliably predict the intelligibility of vocoded (and non-vocoded) Mandarin Chinese is a viable solution to address this challenge. The speech-transmission index (STI) and coherence-based intelligibility measures, among others, have been examined extensively for predicting the intelligibility of English speech but have not been evaluated for vocoded or wideband (non-vocoded) Mandarin speech despite the perceptual differences between the two languages. The results indicated that the coherence-based measures seem to be influenced by the characteristics of the spoken language. The highest correlation (r = 0.91-0.97) was obtained in Mandarin Chinese with a weighted coherence measure that included primarily information from high-intensity voiced segments (e.g., vowels) containing F0 information, known to be important for lexical tone recognition. In contrast, in English, highest correlation was obtained with a coherence measure that included information from weak consonants and vowel/consonant transitions. A band-importance function was proposed that captured information about the amplitude envelope contour. A higher modulation rate (100 Hz) was found necessary for the STI-based measures for maximum correlation (r = 0.94-0.96) with vocoded Mandarin and English recognition.

Tone perception and production in pediatric cochlear implants users

CONCLUSIONS

In prelingually deaf children with cochlear implants, tone perception and production performance are highly correlated. This result is consistent with the hypothesis that tone perception is the prerequisite for good tone production.

OBJECTIVES

Previous research has shown remarkable deficits in tone perception and production in native tone language-speaking, prelingually deafened children with cochlear implants. The purpose of the present study was to investigate the relationship between tone perception and production in those children.

METHODS

Twenty-five prelingually deaf children with cochlear implants participated in the study. All subjects were Advanced Bionics CII/90K users with various lengths of implant use. To evaluate tone perception performance, subjects completed a computerized tone contrast test. For tone production performance, an artificial neural network was used to evaluate the accuracy of tones recorded from each of the 25 subjects.

RESULTS

Large individual differences in tone perception and production performance were observed in these subjects. Tone perception accuracy ranged from 50.0 to 96.9% correct (chance performance = 50% correct; mean = 71.0% correct). Tone production performance ranged from 19.4 to 97.2% correct (mean = 52.0% correct). A strong correlation was found between tone perception and production performance in this group of subjects (r = 0.805).

Musical pitch and lexical tone perception with cochlear implants

OBJECTIVE

The purpose of the present study was to test the hypothesis that cochlear implant (CI) users' music perception is correlated with their lexical tone perception, and the two types of perception share similar mechanisms in electric hearing.

DESIGN

A lexical tone perception test and a pitch interval discrimination test were administered to a group of CI users and a group of normal-hearing (NH) listeners. SAMPLE STUDY: Nineteen adult CI users and 10 NH listeners who are native-Mandarin-Chinese speakers participated in the study.

RESULT

Tone-perception performance of the CI group was, on average, 58.3% correct (± 19.78% correct), and performance of the NH group was near perfect. The CI group had a mean threshold of 5.66 semitones (± 5.57 semitones) in pitch discrimination as compared to the threshold of 0.44 semitone from the NH group. There was a strong correlation between the CI users' tone-perception performance and their pitch discrimination threshold (r = -0.75, p < 0.001).

CONCLUSION

Musical and lexical pitch perceptions are strongly correlated with each other and they might share similar mechanisms in electric hearing.

Vocal singing by prelingually-deafened children with cochlear implants

The coarse pitch information in cochlear implants might hinder the development of singing in prelingually-deafened pediatric users. In the present study, seven prelingually-deafened children with cochlear implants (5.4-12.3 years old) sang one song that was the most familiar to him or her. The control group consisted of 14 normal-hearing children (4.1-8.0 years old). The fundamental frequencies (F0) of each note in the recorded songs were extracted. The following five metrics were computed based on the reference music scores: (1) F0 contour direction of the adjacent notes, (2) F0 compression ratio of the entire song, (3) mean deviation of the normalized F0 across the notes, (4) mean deviation of the pitch intervals, and (5) standard deviation of the note duration differences. Children with cochlear implants showed significantly poorer performance in the pitch-based assessments than the normal-hearing children. No significant differences were seen between the two groups in the rhythm-based measure. Prelingually-deafened children with cochlear implants have significant deficits in singing due to their inability to manipulate pitch in the correct directions and to produce accurate pitch height. Future studies with a large sample size are warranted in order to account for the large variability in singing performance.