Mandarin Chinese tone identification in cochlear implants: predictions from acoustic models

Combination and Comparison of Sound Coding Strategies Using Cochlear Implant Simulation With Mandarin Speech

Three cochlear implant (CI) sound coding strategies were combined in the same signal processing path and compared for speech intelligibility with vocoded Mandarin sentences. The three CI coding strategies, biologically-inspired hearing aid algorithm (BioAid), envelope enhancement (EE), and fundamental frequency modulation (F0mod), were combined with the advanced combination encoder (ACE) strategy. Hence, four singular coding strategies and four combinational coding strategies were derived. Mandarin sentences with speech-shape noise were processed using these coding strategies. Speech understanding of vocoded Mandarin sentences was evaluated using short-time objective intelligibility (STOI) and subjective sentence recognition tests with normal-hearing listeners. For signal-to-noise ratios at 5 dB or above, the EE strategy had slightly higher average scores in both STOI and listening tests compared to ACE. The addition of EE to BioAid slightly increased the mean scores for BioAid+EE, which was the combination strategy with the highest scores in both objective and subjective speech intelligibility. The benefits of BioAid, F0mod, and the four combinational coding strategies were not observed in CI simulation. The findings of this study may be useful for the future design of coding strategies and related studies with Mandarin.

Bimodal Benefits Revealed by Categorical Perception of Lexical Tones in Mandarin-Speaking Kindergarteners With a Cochlear Implant and a Contralateral Hearing Aid

Purpose Pitch reception poses challenges for individuals with cochlear implants (CIs), and adding a hearing aid (HA) in the nonimplanted ear is potentially beneficial. The current study used fine-scale synthetic speech stimuli to investigate the bimodal benefit for lexical tone categorization in Mandarin-speaking kindergarteners using a CI and an HA in opposite ears. Method The data were collected from 16 participants who were required to complete two classical tasks for speech categorical perception (CP) with CI + HA device condition and CI alone condition. Linear mixed-effects models were constructed to evaluate the identification and discrimination scores across different device conditions. Results The bimodal kindergarteners showed CP for the continuum varying from Mandarin Tone 1 and Tone 2. Moreover, the additional acoustic information from the contralateral HA contributes to improved lexical tone categorization, with a steeper slope, a higher discrimination score of between-category stimuli pair, and an improved peakedness score (i.e., an increased benefit magnitude for discriminations of between-category over within-category pairs) for the CI + HA condition than the CI alone condition. The bimodal kindergarteners with better residual hearing thresholds at 250 Hz level in the nonimplanted ear could perceive lexical tones more categorically. Conclusion The enhanced CP results with bimodal listening provide clear evidence for the clinical practice to fit a contralateral HA in the nonimplanted ear in kindergarteners with unilateral CIs with direct benefits from the low-frequency acoustic hearing.

Voice Discrimination by Adults with Cochlear Implants: the Benefits of Early Implantation for Vocal-Tract Length Perception

Cochlear implant (CI) users find it extremely difficult to discriminate between talkers, which may partially explain why they struggle to understand speech in a multi-talker environment. Recent studies, based on findings with postlingually deafened CI users, suggest that these difficulties may stem from their limited use of vocal-tract length (VTL) cues due to the degraded spectral resolution transmitted by the CI device. The aim of the present study was to assess the ability of adult CI users who had no prior acoustic experience, i.e., prelingually deafened adults, to discriminate between resynthesized "talkers" based on either fundamental frequency (F0) cues, VTL cues, or both. Performance was compared to individuals with normal hearing (NH), listening either to degraded stimuli, using a noise-excited channel vocoder, or non-degraded stimuli. Results show that (a) age of implantation was associated with VTL but not F0 cues in discriminating between talkers, with improved discrimination for those subjects who were implanted at earlier age; (b) there was a positive relationship for the CI users between VTL discrimination and speech recognition score in quiet and in noise, but not with frequency discrimination or cognitive abilities; (c) early-implanted CI users showed similar voice discrimination ability as the NH adults who listened to vocoded stimuli. These data support the notion that voice discrimination is limited by the speech processing of the CI device. However, they also suggest that early implantation may facilitate sensory-driven tonotopicity and/or improve higher-order auditory functions, enabling better perception of VTL spectral cues for voice discrimination.

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.

Speech recognition outcomes in Mandarin-speaking cochlear implant users with fine structure processing

CONCLUSION

Mandarin-speaking adults can use the Fine Structure Processing (FSP) coding strategy as well as the Continuous Interleaved Sampling (CIS+) coding strategy. No loss in performance was observed after switch-over. Tone identification improves over time with the FSP coding strategy, which is of benefit to tonal-language users. After some time, fine structure was preferred.

OBJECTIVE

This study aimed to determine speech perception, tone perception, and the subjective preferences of Mandarin-speaking adults who received the FSP coding strategy, at upgrade from the CIS + coding strategy.

METHODS

Thirteen Mandarin-speaking subjects were tested at switch-over from CIS + to the FSP coding strategy ∼1-month after switch-over, 2-months after switch-over, and 3-months after switch-over with the Mandarin Hearing in Noise Test (M-HINT), the Mandarin Tone Identification in Noise Test (M-TINT), and a visual analogue scale assessing Sound and Speech Assessment (SSA).

RESULTS

There were no significant differences in the M-HINT between presentation levels (62 dB SPL vs 65 dB SPL), over time, nor when compared to the CIS + coding strategy. Tone perception improved significantly over time with the FSP coding strategy. Subjects rated the FSP coding strategy with the OPUS 2 as significantly more 'full' and 'rich' than with the CIS + coding strategy after 3-months.

Melodic pitch perception and lexical tone perception in Mandarin-speaking cochlear implant users

OBJECTIVES

To examine the relationship between lexical tone perception and melodic pitch perception in Mandarin-speaking cochlear implant (CI) users and to investigate the influence of previous acoustic hearing on CI users' speech and music perception.

DESIGN

Lexical tone perception and melodic contour identification (MCI) were measured in 21 prelingual and 11 postlingual young (aged 6-26 years) Mandarin-speaking CI users. Lexical tone recognition was measured for four tonal patterns: tone 1 (flat F0), tone 2 (rising F0), tone 3 (falling-rising F0), and tone 4 (falling F0). MCI was measured using nine five-note melodic patterns that contained changes in pitch contour, as well as different semitone spacing between notes.

RESULTS

Lexical tone recognition was generally good (overall mean = 81% correct), and there was no significant difference between subject groups. MCI performance was generally poor (mean = 23% correct). MCI performance was significantly better for postlingual (mean = 32% correct) than for prelingual CI participants (mean = 18% correct). After correcting for outliers, there was no significant correlation between lexical tone recognition and MCI performance for prelingual or postlingual CI participants. Age at deafness was significantly correlated with MCI performance only for postlingual participants. CI experience was significantly correlated with MCI performance for both prelingual and postlingual participants. Duration of deafness was significantly correlated with tone recognition only for prelingual participants.

CONCLUSIONS

Despite the prevalence of pitch cues in Mandarin, the present CI participants had great difficulty perceiving melodic pitch. The availability of amplitude and duration cues in lexical tones most likely compensated for the poor pitch perception observed with these CI listeners. Previous acoustic hearing experience seemed to benefit postlingual CI users' melodic pitch perception. Longer CI experience was associated with better MCI performance for both subject groups, suggesting that CI users' music perception may improve as they gain experience with their device.

Cochlear implants with fine structure processing improve speech and tone perception in Mandarin-speaking adults

CONCLUSION

This study indicates that Mandarin-speaking subjects acquire significant benefit from a cochlear implant (CI) and audio processor with the fine structure processing (FSP) coding strategy. It can take adult Mandarin CI users time to become accustomed to their CI and appreciate the benefits.

OBJECTIVES

This study aimed to determine speech perception outcomes in Mandarin-speaking adults who received the FSP coding strategy.

METHODS

This was a prospective study. Ten adults who were implanted unilaterally with a PULSARCI(100), and received an OPUS 1 or OPUS 2 speech processor, were included in this study. The mean age at implantation was 31.1 years. We determined the benefit to postlingually deafened Mandarin-speaking adults with a severe to profound hearing loss using the tests: monosyllables in quiet, sentences in quiet and the Mandarin Hearing in Noise Test (MHINT). Tone perception was evaluated using a tone perception test. A visual analog scale (VAS) was used to score sound quality and ease of listening.

RESULTS

The results showed a significant improvement between first fitting and 6 months in all speech tests and in tone perception. The VAS scores showed a significant improvement over 6 months in sound quality and an immediate benefit in ease of listening.

Mandarin Chinese speech recognition by pediatric cochlear implant users

OBJECTIVES

Because of difficulties associated with pediatric speech testing, most pediatric cochlear implant (CI) speech studies necessarily involve basic and simple perceptual tasks. There are relatively few studies regarding Mandarin-speaking pediatric CI users' perception of more difficult speech materials (e.g., words and sentences produced by multiple talkers). Difficult speech materials and tests necessarily require older pediatric CI users, who may have different etiologies of hearing loss, duration of deafness, CI experience. The present study investigated how pediatric CI patient demographics influence speech recognition performance with relatively difficult test materials and methods.

METHODS

In this study, open-set recognition of multi-talker (two males and two females) Mandarin Chinese disyllables and sentences were measured in 37 Mandarin-speaking pediatric CI users. Subjects were grouped according to etiology of deafness and previous acoustic hearing experience. Group 1 subjects were all congenitally deafened with little-to-no acoustic hearing experience. Group 2 subjects were not congenitally deafened and had substantial acoustic hearing experience prior to implantation. Multiple linear regression analyses were performed within each group using subject demographics such as age at implantation and age at testing.

RESULTS

Pediatric CI performance was generally quite good. For Group 1, mean performance was 82.3% correct for disyllables and 82.8% correct for sentences. For Group 2, mean performance was 76.6% correct for disyllables and 84.4% correct for sentences. For Group 1, multiple linear regression analyses showed that age at implantation predicted disyllable recognition, and that age at implantation and age at testing predicted sentence recognition. For Group 2, neither age at implantation nor age at testing predicted disyllable or sentence recognition. Performance was significantly better with the female than with the male talkers.

CONCLUSIONS

Consistent with previous studies' findings, early implantation provided a significant advantage for profoundly deaf children. Performance for both groups was generally quite good for the relatively difficult materials and tasks, suggesting that open-set word and sentence recognition may be useful in evaluating speech performance with older pediatric CI users. Differences in disyllable recognition between Groups 1 and 2 may reflect differences in adaptation to electric stimulation. The Group 1 subjects developed speech patterns exclusively via electric stimulation, while the Group 2 subjects adapted to electric stimulation relative to previous acoustic patterns.

Speech identification in noise: Contribution of temporal, spectral, and visual speech cues

This study investigated the degree to which two types of reduced auditory signals (cochlear implant simulations) and visual speech cues combined for speech identification. The auditory speech stimuli were filtered to have only amplitude envelope cues or both amplitude envelope and spectral cues and were presented with/without visual speech. In Experiment 1, IEEE sentences were presented in quiet and noise. For in-quiet presentation, speech identification was enhanced by the addition of both spectral and visual speech cues. Due to a ceiling effect, the degree to which these effects combined could not be determined. In noise, these facilitation effects were more marked and were additive. Experiment 2 examined consonant and vowel identification in the context of CVC or VCV syllables presented in noise. For consonants, both spectral and visual speech cues facilitated identification and these effects were additive. For vowels, the effect of combined cues was underadditive, with the effect of spectral cues reduced when presented with visual speech cues. Analysis indicated that without visual speech, spectral cues facilitated the transmission of place information and vowel height, whereas with visual speech, they facilitated lip rounding, with little impact on the transmission of place information.