The perception of Cantonese lexical tones by early-deafened cochlear implantees

Meta-analysis on lexical tone recognition in cochlear implant users

OBJECTIVE

Lexical tone plays a vital role in speech communication in tonal languages. This study investigated lexical tone recognition in cochlear implant (CI) users, and identified potential factors that influence lexical tone recognition in the CI population.

DESIGN

We conducted a systematic search across eleven major databases, evaluated the risk of bias in the included studies, and conducted five meta-analyses.

STUDY SAMPLE

Forty studies that utilised a multi-item alternative forced-choice paradigm were included to evaluate the performance of lexical tone recognition in CI users.

RESULTS

CI users performed worse at recognising lexical tones than normal hearing (NH) controls. Furthermore, bimodal stimulation could benefit lexical tone recognition for CI users in both quiet and noisy conditions. Besides, the pooled results showed a negative correlation between tone recognition accuracy and age at implantation, as well as a positive correlation between tone recognition performance and the duration of CI experience.

CONCLUSIONS

This study indicates that CI users could not recognise lexical tones at the same level as the NH population. The bimodal intervention does have a more positive effect than unimodal implantation regardless of the listening environment. Moreover, earlier implantation and longer experience with the CI could facilitate lexical tone recognition.

Prelingually Deaf Children With Cochlear Implants Show Better Perception of Voice Cues and Speech in Competing Speech Than Postlingually Deaf Adults With Cochlear Implants

OBJECTIVES

Postlingually deaf adults with cochlear implants (CIs) have difficulties with perceiving differences in speakers' voice characteristics and benefit little from voice differences for the perception of speech in competing speech. However, not much is known yet about the perception and use of voice characteristics in prelingually deaf implanted children with CIs. Unlike CI adults, most CI children became deaf during the acquisition of language. Extensive neuroplastic changes during childhood could make CI children better at using the available acoustic cues than CI adults, or the lack of exposure to a normal acoustic speech signal could make it more difficult for them to learn which acoustic cues they should attend to. This study aimed to examine to what degree CI children can perceive voice cues and benefit from voice differences for perceiving speech in competing speech, comparing their abilities to those of normal-hearing (NH) children and CI adults.

DESIGN

CI children's voice cue discrimination (experiment 1), voice gender categorization (experiment 2), and benefit from target-masker voice differences for perceiving speech in competing speech (experiment 3) were examined in three experiments. The main focus was on the perception of mean fundamental frequency (F0) and vocal-tract length (VTL), the primary acoustic cues related to speakers' anatomy and perceived voice characteristics, such as voice gender.

RESULTS

CI children's F0 and VTL discrimination thresholds indicated lower sensitivity to differences compared with their NH-age-equivalent peers, but their mean discrimination thresholds of 5.92 semitones (st) for F0 and 4.10 st for VTL indicated higher sensitivity than postlingually deaf CI adults with mean thresholds of 9.19 st for F0 and 7.19 st for VTL. Furthermore, CI children's perceptual weighting of F0 and VTL cues for voice gender categorization closely resembled that of their NH-age-equivalent peers, in contrast with CI adults. Finally, CI children had more difficulties in perceiving speech in competing speech than their NH-age-equivalent peers, but they performed better than CI adults. Unlike CI adults, CI children showed a benefit from target-masker voice differences in F0 and VTL, similar to NH children.

CONCLUSION

Although CI children's F0 and VTL voice discrimination scores were overall lower than those of NH children, their weighting of F0 and VTL cues for voice gender categorization and their benefit from target-masker differences in F0 and VTL resembled that of NH children. Together, these results suggest that prelingually deaf implanted CI children can effectively utilize spectrotemporally degraded F0 and VTL cues for voice and speech perception, generally outperforming postlingually deaf CI adults in comparable tasks. These findings underscore the presence of F0 and VTL cues in the CI signal to a certain degree and suggest other factors contributing to the perception challenges faced by CI adults.

Lexical Access in Preschool Mandarin-Speaking Children With Cochlear Implants

PURPOSE

Children with cochlear implants (CIs) have less experience accessing spoken language. Mandarin Chinese uses pitch information to contrast word meaning, and the signal that the CI devices provide is degraded. Thus, Mandarin-speaking children with CIs may face more challenges in the development of language skills. This study examines preschool Mandarin-speaking children's performance in lexical access. We hypothesized that children with CIs and their peers with normal hearing (NH) have comparable naming ability, but they process phonological or semantic information differently.

METHOD

Twenty children with CIs and 20 age-matched children with NH were tested. The cross-modal visual-auditory picture-word interference paradigm was applied. The distractor was either phonologically related (mao⁵⁵ cat -mao⁵¹ hat), semantically related (mao⁵⁵ cat -shu²¹⁴ mouse) or unrelated (mao⁵⁵ cat -zhi²¹⁴ paper) to the target, and it was aurally presented at four different points in time relative to the picture. Accuracy was compared between the two groups to tap into the children's naming abilities, and reaction time was analyzed to examine the effects of phonological and semantic information.

RESULTS

No group difference in accuracy was found. The phonologically related distractors led to significantly higher accuracy scores and shorter reaction times, whereas the semantically related distractors did not. Unlike the NH group, the CI group did not respond significantly faster or slower in phonologically related condition when the distractor and picture occurred simultaneously. Finally, the CI group made overall quicker responses than the NH group.

CONCLUSIONS

Children with CIs are as successful as children with NH in word retrieval and production, and the two groups both show phonological priming effect and lack semantic effect. However, children with CIs do not process phonological information as early as their NH peers, and they may be more tasks directed and hence make quicker responses.

Recognizing Voices Through a Cochlear Implant: A Systematic Review of Voice Perception, Talker Discrimination, and Talker Identification

OBJECTIVE

Some cochlear implant (CI) users report having difficulty accessing indexical information in the speech signal, presumably due to limitations in the transmission of fine spectrotemporal cues. The purpose of this review article was to systematically review and evaluate the existing research on talker processing in CI users. Specifically, we reviewed the performance of CI users in three types of talker- and voice-related tasks. We also examined the different factors (such as participant, hearing, and device characteristics) that might influence performance in these specific tasks.

DESIGN

We completed a systematic search of the literature with select key words using citation aggregation software to search Google Scholar. We included primary reports that tested (a) talker discrimination, (b) voice perception, and (c) talker identification. Each report must have had at least one group of participants with CIs. Each included study was also evaluated for quality of evidence.

RESULTS

The searches resulted in 1,561 references, which were first screened for inclusion and then evaluated in full. Forty-three studies examining talker discrimination, voice perception, and talker identification were included in the final review. Most studies were focused on postlingually deafened and implanted adult CI users, with fewer studies focused on prelingual implant users. In general, CI users performed above chance in these tasks. When there was a difference between groups, CI users performed less accurately than their normal-hearing (NH) peers. A subset of CI users reached the same level of performance as NH participants exposed to noise-vocoded stimuli. Some studies found that CI users and NH participants relied on different cues for talker perception. Within groups of CI users, there is moderate evidence for a bimodal benefit for talker processing, and there are mixed findings about the effects of hearing experience.

CONCLUSIONS

The current review highlights the challenges faced by CI users in tracking and recognizing voices and how they adapt to it. Although large variability exists, there is evidence that CI users can process indexical information from speech, though with less accuracy than their NH peers. Recent work has described some of the factors that might ease the challenges of talker processing in CI users. We conclude by suggesting some future avenues of research to optimize real-world speech outcomes.

The effect of lexical tone experience on English intonation perception in Mandarin-speaking cochlear-implanted children

To examine the effect of lexical tone experience on English intonation perception in Mandarin-speaking cochlear-implanted children during second language acquisition in Taiwan. A retrospective cohort study. A tertiary referred center. Fourteen children with cochlear implant (CI) in the experimental group, and 9 normal hearing children in the control group were enrolled in this study. Cochlear implantation and hearing rehabilitation. Two speech recognition accuracies were examined: (1) Lexical tone recognition (4-alternative forced choice, AFC), (2) English Sentence Intonation (2AFC). The overall accuracies for tone perception are 61.13% (standard deviation, SD = 10.84%) for CI group and 93.82% (SD = 1.80%) for normal hearing group. Tone 4 and Tone 1 were more easily to be recognized than tone 2 and tone 3 in the pediatric CI recipients (cCI) group. In English intonation perception, the overall accuracies are 61.82% (SD = 16.85%) for CI group, and 97.59% (SD = 4.73%) for normal hearing group. Significant high correlation (R = .919, P ≦ .000) between lexical tone perception and English intonation perception is noted. There is no significant difference for English intonation perception accuracies between Mandarin-speaking cCI (61.82%) and English-speaking cCI (70.13%, P = .11). Mandarin-speaking cochlear-implanted children showed significant deficits in perception of lexical tone and English intonation relative to normal hearing children. There was no tonal language benefit in Mandarin-speaking cochlear-implanted children's English intonation perception, compared to the English-speaking cochlear-implanted peers. For cochlear-implanted children, better lexical tone perception comes with better English intonation perception. Enhancing Mandarin prosodic perception for cochlear-implanted children may benefit their command of intonation in English.

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.

Acoustic Correlates of English Lexical Stress Produced by Chinese Dialect Speakers Compared to Native English Speakers

English second language learners often experience difficulties in producing native-like English lexical stress. It is unknown which acoustic correlates, such as fundamental frequency (F0), duration, and intensity, are the most problematic for Chinese dialect speakers. The present study investigated the prosodic transfer effects of first language (L1) regional dialects on the production of English stress contrasts. Native English speakers (N = 20) and Chinese learners (N = 60) with different dialect backgrounds (Beijing, Changsha, and Guangzhou dialects) produced the same stimulus including both trochaic and iambic patterns. Results showed that (a) all participants produced the stressed syllable with greater values of F0, duration, and intensity; (b) Native speakers of English employed an exquisite combination of F0, duration, and intensity, while the dialect groups transfer their native prosody into their production of English lexical stress, resulting in the deviation or abnormality of acoustic cues. Results suggest that L1 native dialect background is considered as a potentially influential factor which may transfer in L2 speech encoding and decoding process.

Perception of English Stress of Synthesized Words by Three Chinese Dialect Groups

This study investigated the possible prosodic transfer influences native regional dialects may have in the perception of English lexical stress by speakers of three Chinese dialects [Beijing (BJ), Changsha (CS), and Guangzhou (GZ)] compared to 20 American English (AE) speakers. F0, duration, intensity, and vowel reduction were manipulated in nonce disyllabic words. Participants performed four-word sequence recall tasks to identify lexical stress location. They performed better with natural sounds than with manipulated words. This study focused on the performance differences in manipulating words. The results showed that all four-group members performed similarly processing F0 condition nonce words. BJ and CS participants were more accurate than GZ participants in duration and vowel reduction cues. Reaction time (RT) suggested that the processing time of acoustic cues differed significantly across language groups. The findings indicate that first language (L1) dialect effect is robust in second language (L2) stress perception tasks.

Voice Emotion Recognition by Mandarin-Speaking Children with Cochlear Implants

Objectives

Emotional expressions are very important in social interactions. Children with cochlear implants can have voice emotion recognition deficits due to device limitations. Mandarin-speaking children with cochlear implants may face greater challenges than those speaking nontonal languages; the pitch information is not well preserved in cochlear implants, and such children could benefit from child-directed speech, which carries more exaggerated distinctive acoustic cues for different emotions. This study investigated voice emotion recognition, using both adult-directed and child-directed materials, in Mandarin-speaking children with cochlear implants compared with normal hearing peers. The authors hypothesized that both the children with cochlear implants and those with normal hearing would perform better with child-directed materials than with adult-directed materials.

Design

Thirty children (7.17-17 years of age) with cochlear implants and 27 children with normal hearing (6.92-17.08 years of age) were recruited in this study. Participants completed a nonverbal reasoning test, speech recognition tests, and a voice emotion recognition task. Children with cochlear implants over the age of 10 years also completed the Chinese version of the Nijmegen Cochlear Implant Questionnaire to evaluate the health-related quality of life. The voice emotion recognition task was a five-alternative, forced-choice paradigm, which contains sentences spoken with five emotions (happy, angry, sad, scared, and neutral) in a child-directed or adult-directed manner.

Results

Acoustic analyses showed substantial variations across emotions in all materials, mainly on measures of mean fundamental frequency and fundamental frequency range. Mandarin-speaking children with cochlear implants displayed a significantly poorer performance than normal hearing peers in voice emotion perception tasks, regardless of whether the performance is measured in accuracy scores, Hu value, or reaction time. Children with cochlear implants and children with normal hearing were mainly affected by the mean fundamental frequency in speech emotion recognition tasks. Chronological age had a significant effect on speech emotion recognition in children with normal hearing; however, there was no significant correlation between chronological age and accuracy scores in speech emotion recognition in children with implants. Significant effects of specific emotion and test materials (better performance with child-directed materials) in both groups of children were observed. Among the children with cochlear implants, age at implantation, percentage scores of nonverbal intelligence quotient test, and sentence recognition threshold in quiet could predict recognition performance in both accuracy scores and Hu values. Time wearing cochlear implant could predict reaction time in emotion perception tasks among children with cochlear implants. No correlation was observed between the accuracy score in voice emotion perception and the self-reported scores of health-related quality of life; however, the latter were significantly correlated with speech recognition skills among Mandarin-speaking children with cochlear implants.

Conclusions

Mandarin-speaking children with cochlear implants could have significant deficits in voice emotion recognition tasks compared with their normally hearing peers and can benefit from the exaggerated prosody of child-directed speech. The effects of age at cochlear implantation, speech and language development, and cognition could play an important role in voice emotion perception by Mandarin-speaking children with cochlear implants.

Perception of Child-Directed Versus Adult-Directed Emotional Speech in Pediatric Cochlear Implant Users

OBJECTIVES

Cochlear implants (CIs) are remarkable in allowing individuals with severe to profound hearing loss to perceive speech. Despite these gains in speech understanding, however, CI users often struggle to perceive elements such as vocal emotion and prosody, as CIs are unable to transmit the spectro-temporal detail needed to decode affective cues. This issue becomes particularly important for children with CIs, but little is known about their emotional development. In a previous study, pediatric CI users showed deficits in voice emotion recognition with child-directed stimuli featuring exaggerated prosody. However, the large intersubject variability and differential developmental trajectory known in this population incited us to question the extent to which exaggerated prosody would facilitate performance in this task. Thus, the authors revisited the question with both adult-directed and child-directed stimuli.

DESIGN

Vocal emotion recognition was measured using both child-directed (CDS) and adult-directed (ADS) speech conditions. Pediatric CI users, aged 7-19 years old, with no cognitive or visual impairments and who communicated through oral communication with English as the primary language participated in the experiment (n = 27). Stimuli comprised 12 sentences selected from the HINT database. The sentences were spoken by male and female talkers in a CDS or ADS manner, in each of the five target emotions (happy, sad, neutral, scared, and angry). The chosen sentences were semantically emotion-neutral. Percent correct emotion recognition scores were analyzed for each participant in each condition (CDS vs. ADS). Children also completed cognitive tests of nonverbal IQ and receptive vocabulary, while parents completed questionnaires of CI and hearing history. It was predicted that the reduced prosodic variations found in the ADS condition would result in lower vocal emotion recognition scores compared with the CDS condition. Moreover, it was hypothesized that cognitive factors, perceptual sensitivity to complex pitch changes, and elements of each child's hearing history may serve as predictors of performance on vocal emotion recognition.

RESULTS

Consistent with our hypothesis, pediatric CI users scored higher on CDS compared with ADS speech stimuli, suggesting that speaking with an exaggerated prosody-akin to "motherese"-may be a viable way to convey emotional content. Significant talker effects were also observed in that higher scores were found for the female talker for both conditions. Multiple regression analysis showed that nonverbal IQ was a significant predictor of CDS emotion recognition scores while Years using CI was a significant predictor of ADS scores. Confusion matrix analyses revealed a dependence of results on specific emotions; for the CDS condition's female talker, participants had high sensitivity (d' scores) to happy and low sensitivity to the neutral sentences while for the ADS condition, low sensitivity was found for the scared sentences.

CONCLUSIONS

In general, participants had higher vocal emotion recognition to the CDS condition which also had more variability in pitch and intensity and thus more exaggerated prosody, in comparison to the ADS condition. Results suggest that pediatric CI users struggle with vocal emotion perception in general, particularly to adult-directed speech. The authors believe these results have broad implications for understanding how CI users perceive emotions both from an auditory communication standpoint and a socio-developmental perspective.

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.

Singing Proficiency of Members of a Choir Formed by Prelingually Deafened Children With Cochlear Implants

Purpose A group of 10 prelingually deafened children with cochlear implants (CIs) formed a choir and received 21 months of formal music training. The purpose of this study was to evaluate the singing proficiency of these children. Method The participants included all choir members (7 girls and 3 boys, mean age of 9.5 years old) who were unilateral CI users. Meanwhile, 8 age-matched children with normal hearing were recruited as controls and were trained on 1 song for 2 weeks. Individual singing samples without instrument accompaniment were recorded from all participants. The singing samples were subject to acoustic analysis in which the fundamental frequency (F0) of each note was extracted and the duration was measured. Five metrics were developed and computed to quantify the accuracy of their pitch and rhythm performance. The 5 metrics included (a) percent correct of F0 contour direction of adjacent notes, (b) mean deviation of the normalized F0 across the notes, (c) mean deviation of the pitch intervals, (d) mean deviation of adjacent note duration ratio, and (e) mean absolute deviation of note duration. Results The choir members with CIs demonstrated high accuracy in both pitch and tempo measures and performed on par with the children with normal hearing. Early start of music training after implantation and use of bimodal hearing contributed to the development of better music ability in these children with CIs. Conclusion These findings indicated that rigorous music training could facilitate high singing proficiency in prelingually deafened children with CIs.

A tonal-language benefit for pitch in normally-hearing and cochlear-implanted children

In tonal languages, voice pitch inflections change the meaning of words, such that the brain processes pitch not merely as an acoustic characterization of sound but as semantic information. In normally-hearing (NH) adults, this linguistic pressure on pitch appears to sharpen its neural encoding and can lead to perceptual benefits, depending on the task relevance, potentially generalizing outside of the speech domain. In children, however, linguistic systems are still malleable, meaning that their encoding of voice pitch information might not receive as much neural specialization but might generalize more easily to ecologically irrelevant pitch contours. This would seem particularly true for early-deafened children wearing a cochlear implant (CI), who must exhibit great adaptability to unfamiliar sounds as their sense of pitch is severely degraded. Here, we provide the first demonstration of a tonal language benefit in dynamic pitch sensitivity among NH children (using both a sweep discrimination and labelling task) which extends partially to children with CI (i.e., in the labelling task only). Strong age effects suggest that sensitivity to pitch contours reaches adult-like levels early in tonal language speakers (possibly before 6 years of age) but continues to develop in non-tonal language speakers well into the teenage years. Overall, we conclude that language-dependent neuroplasticity can enhance behavioral sensitivity to dynamic pitch, even in extreme cases of auditory degradation, but it is most easily observable early in life.

Suprasegmental Features Are Not Acquired Early: Perception and Production of Monosyllabic Cantonese Lexical Tones in 4- to 6-Year-Old Preschool Children

PURPOSE

Previous studies reported that children acquire Cantonese tones before 3 years of age, supporting the assumption in models of phonological development that suprasegmental features are acquired rapidly and early in children. Yet, recent research found a large disparity in the age of Cantonese tone acquisition. This study investigated Cantonese tone development in 4- to 6-year-old children.

METHOD

Forty-eight 4- to 6-year-old Cantonese-speaking children and 28 mothers of the children labeled 30 pictures representing familiar words in the 6 tones in a picture-naming task and identified pictures representing words in different Cantonese tones in a picture-pointing task. To control for lexical biases in tone assessment, tone productions were low-pass filtered to eliminate lexical information. Five judges categorized the tones in filtered stimuli. Tone production accuracy, tone perception accuracy, and correlation between tone production and perception accuracy were examined.

RESULTS

Children did not start to produce adultlike tones until 5 and 6 years of age. Four-year-olds produced none of the tones with adultlike accuracy. Five- and 6-year-olds attained adultlike productions in 2 (T5 and T6) to 3 (T4, T5, and T6) tones, respectively. Children made better progress in tone perception and achieved higher accuracy in perception than in production. However, children in all age groups perceived none of the tones as accurately as adults, except that T1 was perceived with adultlike accuracy by 6-year-olds. Only weak association was found between children's tone perception and production accuracy.

CONCLUSIONS

Contradicting to the long-held assumption that children acquire lexical tone rapidly and early before the mastery of segmentals, this study found that 4- to 6-year-old children have not mastered the perception or production of the full set of Cantonese tones in familiar monosyllabic words. Larger development was found in children's tone perception than tone production. The higher tone perception accuracy but weak correlation between tone perception and production abilities in children suggested that tone perception accuracy is not sufficient for children's tone production accuracy. The findings have clinical and theoretical implications.

Discrimination of Stochastic Frequency Modulation by Cochlear Implant Users

BACKGROUND

Past work has shown that low-rate frequency modulation (FM) may help preserve signal coherence, aid segmentation at word and syllable boundaries, and benefit speech intelligibility in the presence of a masker.

PURPOSE

This study evaluated whether difficulties in speech perception by cochlear implant (CI) users relate to a deficit in the ability to discriminate among stochastic low-rate patterns of FM.

RESEARCH DESIGN

RESEARCH DESIGN

This is a correlational study assessing the association between the ability to discriminate stochastic patterns of low-rate FM and the intelligibility of speech in noise.

STUDY SAMPLE

Thirteen postlingually deafened adult CI users participated in this study.

DATA COLLECTION AND ANALYSIS

Using modulators derived from 5-Hz lowpass noise applied to a 1-kHz carrier, thresholds were measured in terms of frequency excursion both in quiet and with a speech-babble masker present, stimulus duration, and signal-to-noise ratio in the presence of a speech-babble masker. Speech perception ability was assessed in the presence of the same speech-babble masker. Relationships were evaluated with Pearson product-moment correlation analysis with correction for family-wise error, and commonality analysis to determine the unique and common contributions across psychoacoustic variables to the association with speech ability.

RESULTS

Significant correlations were obtained between masked speech intelligibility and three metrics of FM discrimination involving either signal-to-noise ratio or stimulus duration, with shared variance among the three measures accounting for much of the effect. Compared to past results from young normal-hearing adults and older adults with either normal hearing or a mild-to-moderate hearing loss, mean FM discrimination thresholds obtained from CI users were higher in all conditions.

CONCLUSIONS

The ability to process the pattern of frequency excursions of stochastic FM may, in part, have a common basis with speech perception in noise. Discrimination of differences in the temporally distributed place coding of the stimulus could serve as this common basis for CI users.

Perception of Cantonese Lexical Tones by Pediatric Cochlear Implant Users

PURPOSE

The purpose of this study is to assess Cantonese word recognition and the discrimination of Cantonese tones with manipulated contours by child and adolescent cochlear implant (CI) users and a group of peers with normal hearing (NH). It was hypothesized that the CI users would perform more poorly than their counterparts with NH in both tasks and that CI users implanted before 2 years of age would perform better than those implanted after 2 years.

METHOD

Forty-one participants were recruited from hospitals, schools, and kindergartens in Hong Kong: Ten CI users implanted at or before 2 years of age ("early" CI group), 13 CI users implanted after 2 years of age ("late" CI group), and 18 individuals with NH. The mean age at implantation of the early CI group was 1.5 years (SD = 0.3), and for the late CI group, it was 4.3 years (SD = 2.1). Participants were a mean of 13.3 years of age (SD = 3.7) at time of testing. Participants completed a Cantonese word recognition test and a discrimination task using Cantonese tones with modified fundamental frequency trajectories.

RESULTS

Both CI user groups obtained significantly lower scores than the group with NH on the word recognition test. Mean percent correct scores for the word recognition test were 79% for the early CI group, 69% for the late CI group, and 97% for the group with NH. The group with NH consistently achieved higher scores than the CI user groups when discriminating manipulated Cantonese tones. Increasing the acoustic difference between tones improved discrimination performance for CI users for level tone contrasts only. CI users implanted at or before 2 years of age obtained higher scores than those implanted later.

CONCLUSIONS

The results of this study add further evidence that children using CIs do not perform as well as peers in perceiving Cantonese tones. Modification of tones to increase pitch range did not consistently improve the ability of children with implants to perceive the difference between tones. Further research is required to fully assess potential benefits of early implantation for speakers of tonal languages.

SUPPLEMENTAL MATERIALS

https://doi.org/10.23641/asha.5782209.

Voice emotion perception and production in cochlear implant users

Voice emotion is a fundamental component of human social interaction and social development. Unfortunately, cochlear implant users are often forced to interface with highly degraded prosodic cues as a result of device constraints in extraction, processing, and transmission. As such, individuals with cochlear implants frequently demonstrate significant difficulty in recognizing voice emotions in comparison to their normal hearing counterparts. Cochlear implant-mediated perception and production of voice emotion is an important but relatively understudied area of research. However, a rich understanding of the voice emotion auditory processing offers opportunities to improve upon CI biomedical design and to develop training programs benefiting CI performance. In this review, we will address the issues, current literature, and future directions for improved voice emotion processing in cochlear implant users.

Low-frequency fine-structure cues allow for the online use of lexical stress during spoken-word recognition in spectrally degraded speech

English listeners use suprasegmental cues to lexical stress during spoken-word recognition. Prosodic cues are, however, less salient in spectrally degraded speech, as provided by cochlear implants. The present study examined how spectral degradation with and without low-frequency fine-structure information affects normal-hearing listeners' ability to benefit from suprasegmental cues to lexical stress in online spoken-word recognition. To simulate electric hearing, an eight-channel vocoder spectrally degraded the stimuli while preserving temporal envelope information. Additional lowpass-filtered speech was presented to the opposite ear to simulate bimodal hearing. Using a visual world paradigm, listeners' eye fixations to four printed words (target, competitor, two distractors) were tracked, while hearing a word. The target and competitor overlapped segmentally in their first two syllables but mismatched suprasegmentally in their first syllables, as the initial syllable received primary stress in one word and secondary stress in the other (e.g., "'admiral," "'admi'ration"). In the vocoder-only condition, listeners were unable to use lexical stress to recognize targets before segmental information disambiguated them from competitors. With additional lowpass-filtered speech, however, listeners efficiently processed prosodic information to speed up online word recognition. Low-frequency fine-structure cues in simulated bimodal hearing allowed listeners to benefit from suprasegmental cues to lexical stress during word recognition.

Tone Perception of Cantonese-Speaking Prelingually Hearing-Impaired Children with Cochlear Implants

OBJECTIVE: To evaluate tone perception performance in Cantonese-speaking prelingually hearing-impaired children with cochlear implants.

STUDY DESIGN AND SETTING: The ability to discriminate and identify Cantonese tones was evaluated on 17 native Cantonese-speaking prelingually hearing-impaired children. Performance was correlated to factors like age of implantation and general communication ability.

RESULTS: Subjects' performance in discrimination and identification tasks was slightly above chance level. Although variations in the contour fundamental frequency of the tones provided some cues for tone discrimination, these distinctions proved insufficient for subjects to perform well. Tone 6 (low level tone) was the most difficult to identify. Subjects' performance did not correlate with gender, age of implantation, duration of implant use, frequency of auditory training session, or general communication ability.

CONCLUSION: Although some children were able to discriminate and/or identify Cantonese tones, their performance was poor. Further studies are needed to understand how tone perception relate to daily speech understanding.

SIGNIFICANCE: Cochlear implant speech coding strategies may need modification to optimize tone perception. (Otolaryngol Head Neck Surg 2004; 130:751-8.)

Mandarin Lexical Tone Acquisition in Cochlear Implant Users With Prelingual Deafness: A Review

PURPOSE

The purpose of this review article is to synthesize evidence from the fields of developmental linguistics and cochlear implant technology relevant to the production and perception of Mandarin lexical tone in cochlear implant users with prelingual deafness. The aim of this review was to identify potential factors that determine outcomes for tonal-language speaking cochlear implant users and possible directions for further research.

METHOD

A computerized database search of MEDLINE, CINAHL, Academic Search Premier, Web of Science, and Google Scholar was undertaken in June and July 2014. Search terms used were lexical tone AND tonal language, speech development AND/OR speech production AND/OR speech perception AND cochlear implants, and pitch perception AND cochlear implants, anywhere in the title or abstract.

CONCLUSION

Despite the demonstrated limitations of pitch perception in cochlear implant users, there is some evidence that typical production and perception of lexical tone is possible by cochlear implant users with prelingual deafness. Further studies are required to determine the factors that contribute to better outcomes to inform rehabilitation processes for cochlear implant users in tonal-language environments.

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.

Loudness Contour Can Influence Mandarin Tone Recognition: Vocoder Simulation and Cochlear Implants

Lexical tone recognition with current cochlear implants (CI) remains unsatisfactory due to significantly degraded pitch-related acoustic cues, which dominate the tone recognition by normal-hearing (NH) listeners. Several secondary cues (e.g., amplitude contour, duration, and spectral envelope) that influence tone recognition in NH listeners and CI users have been studied. This work proposes a loudness contour manipulation algorithm, namely Loudness-Tone (L-Tone), to investigate the effects of loudness contour on Mandarin tone recognition and the effectiveness of using loudness cue to enhance tone recognition for CI users. With L-Tone, the intensity of sound samples is multiplied by gain values determined by instantaneous fundamental frequencies (F0s) and pre-defined gain- F0 mapping functions. Perceptual experiments were conducted with a four-channel noise-band vocoder simulation in NH listeners and with CI users. The results suggested that 1) loudness contour is a useful secondary cue for Mandarin tone recognition, especially when pitch cues are significantly degraded; 2) L-Tone can be used to improve Mandarin tone recognition in both simulated and actual CI-hearing without significant negative effect on vowel and consonant recognition. L-Tone is a promising algorithm for incorporation into real-time CI processing and off-line CI rehabilitation training software.

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.

Deficits in the Sensitivity to Pitch Sweeps by School-Aged Children Wearing Cochlear Implants

Sensitivity to static changes in pitch has been shown to be poorer in school-aged children wearing cochlear implants (CIs) than children with normal hearing (NH), but it is unclear whether this is also the case for dynamic changes in pitch. Yet, dynamically changing pitch has considerable ecological relevance in terms of natural speech, particularly aspects such as intonation, emotion, or lexical tone information. Twenty one children with NH and 23 children wearing a CI participated in this study, along with 18 NH adults and 6 CI adults for comparison. Listeners with CIs used their clinically assigned settings with envelope-based coding strategies. Percent correct was measured in one- or three-interval two-alternative forced choice tasks, for the direction or discrimination of harmonic complexes based on a linearly rising or falling fundamental frequency. Sweep rates were adjusted per subject, in a logarithmic scale, so as to cover the full extent of the psychometric function. Data for up- and down-sweeps were fitted separately, using a maximum-likelihood technique. Fits were similar for up- and down-sweeps in the discrimination task, but diverged in the direction task because psychometric functions for down-sweeps were very shallow. Hits and false alarms were then converted into d′ and beta values, from which a threshold was extracted at a d′ of 0.77. Thresholds were very consistent between the two tasks and considerably higher (worse) for CI listeners than for their NH peers. Thresholds were also higher for children than adults. Factors such as age at implantation, age at profound hearing loss, and duration of CI experience did not play any major role in this sensitivity. Thresholds of dynamic pitch sensitivity (in either task) also correlated with thresholds for static pitch sensitivity and with performance in tasks related to speech prosody.

Voice emotion recognition by cochlear-implanted children and their normally-hearing peers

Despite their remarkable success in bringing spoken language to hearing impaired listeners, the signal transmitted through cochlear implants (CIs) remains impoverished in spectro-temporal fine structure. As a consequence, pitch-dominant information such as voice emotion, is diminished. For young children, the ability to correctly identify the mood/intent of the speaker (which may not always be visible in their facial expression) is an important aspect of social and linguistic development. Previous work in the field has shown that children with cochlear implants (cCI) have significant deficits in voice emotion recognition relative to their normally hearing peers (cNH). Here, we report on voice emotion recognition by a cohort of 36 school-aged cCI. Additionally, we provide for the first time, a comparison of their performance to that of cNH and NH adults (aNH) listening to CI simulations of the same stimuli. We also provide comparisons to the performance of adult listeners with CIs (aCI), most of whom learned language primarily through normal acoustic hearing. Results indicate that, despite strong variability, on average, cCI perform similarly to their adult counterparts; that both groups' mean performance is similar to aNHs' performance with 8-channel noise-vocoded speech; that cNH achieve excellent scores in voice emotion recognition with full-spectrum speech, but on average, show significantly poorer scores than aNH with 8-channel noise-vocoded speech. A strong developmental effect was observed in the cNH with noise-vocoded speech in this task. These results point to the considerable benefit obtained by cochlear-implanted children from their devices, but also underscore the need for further research and development in this important and neglected area. This article is part of a Special Issue entitled .

Cantonese tone production performance of mainstream school children with hearing impairment

This study investigated the Cantonese tone production ability of children with hearing impairment studying in mainstream schools. The participants were 87 Cantonese-speaking children with mild-to-profound degrees of hearing loss aged 5.92-13.58 in Hong Kong. Most of the children were fitted with hearing aids (n = 65); 17 of them had profound hearing impairment, one who had severe hearing loss had cochlear implantation, and four who had mild hearing loss were without any hearing device. The Hong Kong Cantonese Articulation Test was administered, and the tones produced were rated by two of the authors and a speech-language pathologist. Group effects of tones, hearing loss level, and also an interaction of the two were found to be significant. The children with profound hearing impairment performed significantly worse than most of the other children. Tone 1 was produced most accurately, whereas tone 6 productions were the poorest. No relationship was found between the number of years of mainstreaming and tone production ability. Tone production error pattern revealed that confusion patterns in tone perception coincided with those in production. Tones having a similar fundamental frequency (F0) at the onset also posed difficulty in tone production for children with hearing impairment.

The effect of enhancing temporal periodicity cues on Cantonese tone recognition by cochlear implantees

OBJECTIVES

This study investigates the efficacy of a cochlear implant (CI) processing method that enhances temporal periodicity cues of speech.

DESIGN

Subjects participated in word and tone identification tasks. Two processing conditions - the conventional advanced combination encoder (ACE) and tone-enhanced ACE were tested. Test materials were Cantonese disyllabic words recorded from one male and one female speaker. Speech-shaped noise was added to clean speech. The fundamental frequency information for periodicity enhancement was extracted from the clean speech. Electrical stimuli generated from the noisy speech with and without periodicity enhancement were presented via direct stimulation using a Laura 34 research processor. Subjects were asked to identify the presented word.

STUDY SAMPLE

Seven post-lingually deafened native Cantonese-speaking CI users.

RESULTS

Percent correct word, segmental structure, and tone identification scores were calculated. While word and segmental structure identification accuracy remained similar between the two processing conditions, tone identification in noise was better with tone-enhanced ACE than with conventional ACE. Significant improvement on tone perception was found only for the female voice.

CONCLUSIONS

Temporal periodicity cues are important to tone perception in noise. Pitch and tone perception by CI users could be improved when listeners received enhanced temporal periodicity cues.

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.

Enhancement of temporal cues to pitch in cochlear implants: effects on pitch ranking

The abilities to hear changes in pitch for sung vowels and understand speech using an experimental sound coding strategy (eTone) that enhanced coding of temporal fundamental frequency (F0) information were tested in six cochlear implant users, and compared with performance using their clinical (ACE) strategy. In addition, rate- and modulation rate-pitch difference limens (DLs) were measured using synthetic stimuli with F0s below 300 Hz to determine psychophysical abilities of each subject and to provide experience in attending to rate cues for the judgment of pitch. Sung-vowel pitch ranking tests for stimuli separated by three semitones presented across an F0 range of one octave (139-277 Hz) showed a significant benefit for the experimental strategy compared to ACE. Average d-prime (d') values for eTone (d' = 1.05) were approximately three time larger than for ACE (d' = 0.35). Similar scores for both strategies in the speech recognition tests showed that coding of segmental speech information by the experimental strategy was not degraded. Average F0 DLs were consistent with results from previous studies and for all subjects were less than or equal to approximately three semitones for F0s of 125 and 200 Hz.

Acoustic cue integration in speech intonation recognition with cochlear implants

The present article reports on the perceptual weighting of prosodic cues in question-statement identification by adult cochlear implant (CI) listeners. Acoustic analyses of normal-hearing (NH) listeners' production of sentences spoken as questions or statements confirmed that in English the last bisyllabic word in a sentence carries the dominant cues (F0, duration, and intensity patterns) for the contrast. Furthermore, these analyses showed that the F0 contour is the primary cue for the question-statement contrast, with intensity and duration changes conveying important but less reliable information. On the basis of these acoustic findings, the authors examined adult CI listeners' performance in two question-statement identification tasks. In Task 1, 13 CI listeners' question-statement identification accuracy was measured using naturally uttered sentences matched for their syntactic structures. In Task 2, the same listeners' perceptual cue weighting in question-statement identification was assessed using resynthesized single-word stimuli, within which fundamental frequency (F0), intensity, and duration properties were systematically manipulated. Both tasks were also conducted with four NH listeners with full-spectrum and noise-band-vocoded stimuli. Perceptual cue weighting was assessed by comparing the estimated coefficients in logistic models fitted to the data. Of the 13 CI listeners, 7 achieved high performance levels in Task 1. The results of Task 2 indicated that multiple sources of acoustic cues for question-statement identification were utilized to different extents depending on the listening conditions (e.g., full spectrum vs. spectrally degraded) or the listeners' hearing and amplification status (e.g., CI vs. NH).

Phonological awareness of Cantonese-speaking pre-school children with cochlear implants

The study investigated the phonological awareness abilities of Cantonese-speaking pre-schoolers with cochlear implants. Participants were 15 Cantonese-speaking children with cochlear implants (CIs) aged 3.08-6.10, chronological-age-matched with 15 children with normal hearing. Each participant performed 10 tasks evaluating different levels of phonological awareness abilities and phonological knowledge. The results showed that pre-schoolers with cochlear implants and their normal hearing peers had similar levels of syllable awareness, phoneme awareness and rhyme awareness. However, cochlear implant users showed significantly poorer performance on tone awareness and phonological knowledge tasks than their normal hearing peers. Cantonese-speaking pre-schoolers with cochlear implants were able to develop phonological awareness. However, the cochlear implants might not provide enough tonal information for children with hearing impairment for tonal lexical comprehension. Incomplete speech and language stimulation may affect phonological knowledge development in Cantonese-speaking pre-schoolers with cochlear implants.

Effect of cochlear implants on children's perception and production of speech prosody

Japanese 5- to 13-yr-olds who used cochlear implants (CIs) and a comparison group of normally hearing (NH) Japanese children were tested on their perception and production of speech prosody. For the perception task, they were required to judge whether semantically neutral utterances that were normalized for amplitude were spoken in a happy, sad, or angry manner. The performance of NH children was error-free. By contrast, child CI users performed well below ceiling but above chance levels on happy- and sad-sounding utterances but not on angry-sounding utterances. For the production task, children were required to imitate stereotyped Japanese utterances expressing disappointment and surprise as well as culturally typically representations of crow and cat sounds. NH 5- and 6-year-olds produced significantly poorer imitations than older hearing children, but age was unrelated to the imitation quality of child CI users. Overall, child CI user's imitations were significantly poorer than those of NH children, but they did not differ significantly from the imitations of the youngest NH group. Moreover, there was a robust correlation between the performance of child CI users on the perception and production tasks; this implies that difficulties with prosodic perception underlie their difficulties with prosodic imitation.

Faciliation of Mandarin tone perception by visual speech in clear and degraded audio: implications for cochlear implants

Cochlear implant (CI) users in tone language environments report great difficulty in perceiving lexical tone. This study investigated the augmentation of simulated cochlear implant audio by visual (facial) speech information for tone. Native speakers of Mandarin and Australian English were asked to discriminate between minimal pairs of Mandarin tones in five conditions: Auditory-Only, Auditory-Visual, CI-simulated Auditory-Only, CI-simulated Auditory-Visual, and Visual-Only (silent video). Discrimination in CI-simulated audio conditions was poor compared with normal audio, and varied according to tone pair, with tone pairs with strong non-F0 cues discriminated the most easily. The availability of visual speech information also improved discrimination in the CI-simulated audio conditions, particularly on tone pairs with strong durational cues. In the silent Visual-Only condition, both Mandarin and Australian English speakers discriminated tones above chance levels. Interestingly, tone-naïve listeners outperformed native listeners in the Visual-Only condition, suggesting firstly that visual speech information for tone is available, and may in fact be under-used by normal-hearing tone language perceivers, and secondly that the perception of such information may be language-general, rather than the product of language-specific learning. This may find application in the development of methods to improve tone perception in CI users in tone language environments.

Children's development of intonation during the first year of cochlear implant experience

This article describes the longitudinal development of intonation in 18 deaf children who received cochlear implants (CIs) before the age of 3 years and 12 infants with typical development (TD) who served as controls. At the time their implants were activated, the children with CIs ranged in age from 9 to 36 months. Cross-group comparisons were made when the children had equivalent amounts of robust hearing experience but different chronological ages. This article reports the results for the 6-month period ending 9 months after activation of the child's device for children with CIs, and the 6-month period ending at 12 months of age for TD infants. The findings were compared with a model of early intonation development in children with normal hearing. The results indicated that all groups progressed through one or more of the stages predicted by the normative model. At the end of the study period, however, children who had received a CI later than 24 months reached a more mature stage of intonation development than younger CI recipients. Moreover, the older CI group reached the same stage of development as the TD infants who had 3 additional months of language listening experience. The findings suggest that the developmental advantage which older children had previously demonstrated shortly after activation of their CIs is maintained throughout most or all of the first year of CI use.

Acoustic characteristics of vowels and plosives/affricates of Mandarin-speaking hearing-impaired children

This article presents the results of an acoustic analysis of vowels and plosives/affricates produced by 45 Mandarin-speaking children with hearing impairment. Vowel production is represented and categorized into three groups by vowel space size calculated with normalized F1 and F2 values of corner vowels. The correlation between speech intelligibility and language abilities assessed by the level of word comprehension and the complexity of sentence structure is statistically significant. Vowel space grouping is correlated with speech intelligibility and spike percentage of plosives/affricates production. The generalized linear model analysis also shows that the level of word comprehension and the degree of hearing loss are the two most significant factors in predicting speech intelligibility. The statistical results suggest that the interplay of acoustic characteristic and speech ability is complex.

Development of a temporal fundamental frequency coding strategy for cochlear implants

A sound-coding strategy for users of cochlear implants, named enhanced-envelope-encoded tone (eTone), was developed to improve coding of fundamental frequency (F0) in the temporal envelopes of the electrical stimulus signals. It is based on the advanced combinational encoder (ACE) strategy and includes additional processing that explicitly applies F0 modulation to channel envelope signals that contain harmonics of prominent complex tones. Channels that contain only inharmonic signals retain envelopes normally produced by ACE. The strategy incorporates an F0 estimator to determine the frequency of modulation and a harmonic probability estimator to control the amount of modulation enhancement applied to each channel. The F0 estimator was designed to provide an accurate estimate of F0 with minimal processing lag and robustness to the effects of competing noise. Error rates for the F0 estimator and accuracy of the harmonic probability estimator were compared with previous approaches and outcomes demonstrated that the strategy operates effectively across a range of signals and conditions that are relevant to cochlear implant users.

Perception of suprasegmental speech features via bimodal stimulation: cochlear implant on one ear and hearing aid on the other

PURPOSE

The purpose of the study was to evaluate the contribution of acoustic hearing to the perception of suprasegmental features by adults who use a cochlear implant (CI) and a hearing aid (HA) in opposite ears.

METHOD

23 adults participated in this study. Perception of suprasegmental features-intonation, syllable stress, and word emphasis-was assessed. All tests were administered in 2 conditions: CI alone and CI + HA (bimodal).

RESULTS

Scores were significantly higher in the bimodal condition in comparison to scores in CI alone for all 3 tests. In both conditions, there was great variability among the individual participants. Significant negative correlations emerged between perception of suprasegmental features and the unaided pure-tone average of the contralateral ear to the CI.

CONCLUSIONS

This study found a significant bimodal advantage for perception of all suprasegmental features, most probably due to the better low-frequency acoustic hearing that is provided by the HA. Outcomes suggest that in cases of residual hearing in the contralateral ear to the implanted ear, HA use should be encouraged.

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).