Children With Cochlear Implants Recognize Their Mother's Voice

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.

Infants' Mapping of New Faces to New Voices

The ability to identify individuals by voice is fundamental for communication. However, little is known about the expectations that infants hold when learning unfamiliar voices. Here, the voice-learning skills of 4- and 8-month-olds (N = 53; 29 girls, 14 boys of various ethnicities) were tested using a preferential-looking task that involved audiovisual stimuli of their mothers and other unfamiliar women. Findings reveal that the expectation that novel voices map on to novel faces emerges between 4 and 8 months of age, and that infants can retain learning of face-voice pairings via nonostensive cues by 8 months of age. This study provides new insights about infants' use of disambiguation and fast mapping in early voice learning.

The Use of Voice Cues for Speaker Gender Recognition in Cochlear Implant Recipients

PURPOSE

The focus of this study was to examine the influence of fundamental frequency (F0) and vocal tract length (VTL) modifications on speaker gender recognition in cochlear implant (CI) recipients for different stimulus types.

METHOD

Single words and sentences were manipulated using isolated or combined F0 and VTL cues. Using an 11-point rating scale, CI recipients and listeners with normal hearing rated the maleness/femaleness of the corresponding voice.

RESULTS

Speaker gender ratings for combined F0 and VTL modifications were similar across all stimulus types in both CI recipients and listeners with normal hearing, although the CI recipients showed a somewhat larger ambiguity. In contrast to listeners with normal hearing, F0-VTL and F0-only modifications revealed similar ratings in the CI recipients when using words as stimuli. However, when sentences were used, a difference was found between F0-VTL-based and F0-based ratings. Modifying VTL cues alone did not affect ratings in the CI group.

CONCLUSIONS

Whereas speaker gender ratings by listeners with normal hearing relied on combined VTL and F0 cues, CI recipients made only limited use of VTL cues, which might be one reason behind problems with identifying the speaker on the basis of voice. However, use of the voice cues depended on stimulus type, with the greater information in sentences allowing a more detailed analysis than single words in both listener groups.

Children's identification of familiar songs from pitch and timing cues

The goal of the present study was to ascertain whether children with normal hearing and prelingually deaf children with cochlear implants could use pitch or timing cues alone or in combination to identify familiar songs. Children 4–7 years of age were required to identify the theme songs of familiar TV shows in a simple task with excerpts that preserved (1) the relative pitch and timing cues of the melody but not the original instrumentation, (2) the timing cues only (rhythm, meter, and tempo), and (3) the relative pitch cues only (pitch contour and intervals). Children with normal hearing performed at high levels and comparably across the three conditions. The performance of child implant users was well above chance levels when both pitch and timing cues were available, marginally above chance with timing cues only, and at chance with pitch cues only. This is the first demonstration that children can identify familiar songs from monotonic versions—timing cues but no pitch cues—and from isochronous versions—pitch cues but no timing cues. The study also indicates that, in the context of a very simple task, young implant users readily identify songs from melodic versions that preserve pitch and timing cues.

Cross-modal signatures in maternal speech and singing

We explored the possibility of a unique cross-modal signature in maternal speech and singing that enables adults and infants to link unfamiliar speaking or singing voices with subsequently viewed silent videos of the talkers or singers. In Experiment 1, adults listened to 30-s excerpts of speech followed by successively presented 7-s silent video clips, one from the previously heard speaker (different speech content) and the other from a different speaker. They successfully identified the previously heard speaker. In Experiment 2, adults heard comparable excerpts of singing followed by silent video clips from the previously heard singer (different song) and another singer. They failed to identify the previously heard singer. In Experiment 3, the videos of talkers and singers were blurred to obscure mouth movements. Adults successfully identified the talkers and they also identified the singers from videos of different portions of the song previously heard. In Experiment 4, 6- to 8-month-old infants listened to 30-s excerpts of the same maternal speech or singing followed by exposure to the silent videos on alternating trials. They looked longer at the silent videos of previously heard talkers and singers. The findings confirm the individuality of maternal speech and singing performance as well as adults' and infants' ability to discern the unique cross-modal signatures. The cues that enable cross-modal matching of talker and singer identity remain to be determined.

The music perception abilities of prelingually deaf children with cochlear implants

OBJECTIVE

To investigate the music perception abilities of prelingually deaf children with cochlear implants, in comparison to a group of normal-hearing children, and to consider the factors that contribute to music perception.

METHODS

The music perception abilities of 39 prelingually deaf children with unilateral cochlear implants were compared to the abilities of 39 normal hearing children. To assess the music listening abilities, the MuSIC perception test was adopted. The influence of the child's age, age at implantation, device experience and type of sound-processing strategy on the music perception were evaluated. The effects of auditory performance, nonverbal intellectual abilities, as well as the child's additional musical education on music perception were also considered.

RESULTS

Children with cochlear implants and normal hearing children performed significantly differently with respect to rhythm discrimination (55% vs. 82%, p<0.001), instrument identification (57% vs. 88%, p<0.001) and emotion rating (p=0.022). However we found no significant difference in terms of melody discrimination and dissonance rating between the two groups. There was a positive correlation between auditory performance and melody discrimination (r=0.27; p=0.031), between auditory performance and instrument identification (r=0.20; p=0.059) and between the child's grade (mark) in school music classes and melody discrimination (r=0.34; p=0.030). In children with cochlear implant only, the music perception ability assessed by the emotion rating test was negatively correlated to the child's age (r(S)=-0.38; p=0.001), age at implantation (r(S)=-0.34; p=0.032), and device experience (r(S)=-0.38; p=0.019). The child's grade in school music classes showed a positive correlation to music perception abilities assessed by rhythm discrimination test (r(S)=0.46; p<0.001), melody discrimination test (r(S)=0.28; p=0.018), and instrument identification test (r(S)=0.23; p=0.05).

CONCLUSIONS

As expected, there was a marked difference in the music perception abilities of prelingually deaf children with cochlear implants in comparison to the group of normal hearing children, but not for all the tests of music perception. Additional multi-centre studies, including a larger number of participants and a broader spectrum of music subtests, considering as many as possible of the factors that may contribute to music perception, seem reasonable.

Gender identification in younger and older adults: use of spectral and temporal cues in noise-vocoded speech

OBJECTIVE

The aim of this study was to investigate potential effects of age on the ability of normal-hearing (NH) adult listeners to utilize spectral and temporal cues when performing a voice gender identification task.

DESIGN

Ten younger and 10 older NH adult listeners were measured on their ability to correctly identify the speaker gender of six different vowel tokens (H-/vowel/-D) when spoken by eight speakers (four male and four female). Spectral (number of channels) and temporal cues (low-pass cut-off frequency for temporal envelope extraction) were systematically manipulated using noiseband vocoding techniques; stimuli contained 1, 4, 8, 16, or 32 spectral channels, while the low-pass cut-off frequency of the temporal envelope filter was 20, 50, 100, 200, or 400 Hz. Furthermore, the fundamental frequencies (F0s) of the vowel tokens were manipulated to create two conditions: "Expanded" (large range of F0 values) and "Compressed" (small range of F0 values).

RESULTS

In general, younger listeners performed better than the older listeners but only when stimuli were spectrally degraded. For both the Expanded and Compressed conditions, the overall performance of the younger listeners was better than that of the older listeners, suggesting age-related deficits in both spectral and temporal processing. Furthermore, a significant interaction between age group and temporal envelope cues revealed that older listeners received less benefit from increasing temporal envelope information compared with the benefit observed among younger listeners. In particular, the performance of the younger NH group (collapsed across number of channels), but not the older NH group, improved as the temporal envelope cut-off frequency was increased from 50 to 400 Hz.

CONCLUSIONS

The results reported here support previous findings of senescent declines in perceiving spectrally reduced speech and temporal amplitude modulation processing. These results suggest that when F0 values are similar to one another, younger listeners can use temporal cues alone to glean voice-pitch information but older listeners exhibit a lessened ability to use such cues. Previous studies have demonstrated the importance of temporal envelope cues in periodicity perception (e.g., gender recognition) by cochlear implant listeners. The results of this study suggest that aging affects the use of such cues, and consequently gender recognition might be poorer among older cochlear implant recipients.

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.

Age-related changes in talker recognition with reduced spectral cues

Temporal information provided by cochlear implants enables successful speech perception in quiet, but limited spectral information precludes comparable success in voice perception. Talker identification and speech decoding by young hearing children (5-7 yr), older hearing children (10-12 yr), and hearing adults were examined by means of vocoder simulations of cochlear implant processing. In Experiment 1, listeners heard vocoder simulations of sentences from a man, woman, and girl and were required to identify the talker from a closed set. Younger children identified talkers more poorly than older listeners, but all age groups showed similar benefit from increased spectral information. In Experiment 2, children and adults provided verbatim repetition of vocoded sentences from the same talkers. The youngest children had more difficulty than older listeners, but all age groups showed comparable benefit from increasing spectral resolution. At comparable levels of spectral degradation, performance on the open-set task of speech decoding was considerably more accurate than on the closed-set task of talker identification. Hearing children's ability to identify talkers and decode speech from spectrally degraded material sheds light on the difficulty of these domains for child implant users.