Intelligibility of spontaneous conversational speech produced by children with cochlear implants: a review

Measuring speech intelligibility with deaf and hard-of-hearing children: A systematic review

There is great variability in the ways in which the speech intelligibility of d/Deaf and hard-of-hearing (DHH) children who use spoken language as part, or all, of their communication system is measured. This systematic review examined the measures and methods that have been used when examining the speech intelligibility of children who are DHH and the characteristics of these measures and methods. A systematic database search was conducted of CENTRAL; CINAHL; Cochrane; ERIC; Joanna Briggs; Linguistics, Language and Behavior Abstracts; Medline; Scopus; and Web of Science databases, as well as supplemental searches. A total of 204 included studies reported the use of many different measures/methods which measured segmental aspects of speech, with the most common being Allen et al.'s (2001, The reliability of a rating scale for measuring speech intelligibility following pediatric cochlear implantation. Otology and Neurotology, 22(5), 631-633. https://doi.org/10.1097/00129492-200109000-00012) Speech Intelligibility Rating scale. Many studies included insufficient details to determine the measure that was used. Future research should utilize methods/measures with known psychometric validity, provide clear descriptions of the methods/measures used, and consider using more than one measure to account for limitations inherent in different methods of measuring the speech intelligibility of children who are DHH, and consider and discuss the rationale for the measure/method chosen.

Spontaneous speech intelligibility: early cochlear implanted children versus their normally hearing peers at seven years of age

Speaking intelligibly is an important achievement in children's language development. How far do congenitally severe-to-profound hearing-impaired children who received a cochlear implant (CI) in the first two years of their life advance on the path to intelligibility in comparison to children with typical hearing (NH)? Spontaneous speech samples of children with CI and children with NH were orthographically transcribed by naïve transcribers. The entropy of the transcriptions was computed to analyze their degree of uniformity. The same samples were also rated on a continuous rating scale by another group of adult listeners. The transcriptions of the NH children's speech were more uniform, i.e., had significantly lower entropy, than those of the CI children, suggesting that the latter group displayed lower intelligibility. This was confirmed by the ratings on the continuous scale. Despite the relatively restricted age ranges, older children reached better intelligibility scores in both groups.

Auditory, Speech and Language Development in Cochlear Implant Children: A One Year Longitudinal Study

The advent of Cochlear Implants (CI) has bought with it, the goal of spoken language performance for severe-profound sensori-neural hearing loss (SNHL) as par with the normal hearing listeners. The aim of this study was to evaluate the outcome of paediatric cochlear implantation in auditory and speech skills below the age of 5 years. The present study consisted of 50 childrens. Auditory skills were assessed in terms of audiometric thresholds and localization abilities. Speech - Language skills were measured using; Categories of Auditory Performance -CAP; Meaningful Use of Speech Scale - MUSS; Meaningful Auditory Integration Scale - MAIS and Speech intelligibility Rating - SIR. Hearing thresholds obtained from all the subjects for pre implant and post implant conditions of 3rd, 6th, 9th, 12th month conditions, evidenced a high significant (p < 0.001) improvement across all test frequencies 500, 1000, 2000 and 4000 Hz. There was also a statistically significant difference across successive measurements of auditory and speech skills, as determined by ANOVA (F (4, 245) = 151.33, p < 0.001 for CAP; F (4, 245) = 89.636, p < 0.001 for SIR; F (4, 245) = 812.282 p < 0.001 for MAIS and F(4, 245) = 435.677 p < 0.001 for MUSS). Auditory localization abilities were also improved considerably over a period of one year. The present study added the evidence to the literature that cochlear implants significantly improved the hearing ability of children with severe-to-profound hearing loss. This study also demonstrated that, children were better able to make use of the auditory information perceived through the implant.

Auditory feedback experience in the development of phonetic production: Evidence from preschoolers with cochlear implants and their normal-hearing peers

Previous work has found that preschoolers with greater phonological awareness and larger lexicons, who speak more throughout the day, exhibit less intra-syllabic coarticulation in controlled speech production tasks. These findings suggest that both linguistic experience and speech-motor control are important predictors of spoken phonetic development. Still, it remains unclear how preschoolers' speech practice when they talk drives the development of coarticulation because children who talk more are likely to have both increased fine motor control and increased auditory feedback experience. Here, the potential effect of auditory feedback is studied by examining a population-children with cochlear implants (CIs)-which is naturally differing in auditory experience. The results show that (1) developmentally appropriate coarticulation improves with an increased hearing age but not chronological age; (2) children with CIs pattern coarticulatorily closer to their younger, hearing age-matched peers than chronological age-matched peers; and (3) the effects of speech practice on coarticulation, measured using naturalistic, at-home recordings of the children's speech production, only appear in the children with CIs after several years of hearing experience. Together, these results indicate a strong role of auditory feedback experience on coarticulation and suggest that parent-child communicative exchanges could stimulate children's own vocal output, which drives speech development.

Vowel Production in Prelingually Deafened Mandarin-Speaking Children With Cochlear Implants

Purpose The purpose of this study was to characterize the acoustic profile and to evaluate the intelligibility of vowel productions in prelingually deafened, Mandarin-speaking children with cochlear implants (CIs). Method Twenty-five children with CIs and 20 age-matched children with normal hearing (NH) were recorded producing a list of Mandarin disyllabic and trisyllabic words containing 20 Mandarin vowels [a, i, u, y, ɤ, ɿ, ʅ, ai, ei, ia, ie, ye, ua, uo, au, ou, iau, iou, uai, uei] located in the first consonant-vowel syllable. The children with CIs were all prelingually deafened and received unilateral implantation before 7 years of age with an average length of CI use of 4.54 years. In the acoustic analysis, the first two formants (F1 and F2) were extracted at seven equidistant time locations for the tested vowels. The durational and spectral features were compared between the CI and NH groups. In the vowel intelligibility task, the extracted vowel portions in both NH and CI children were presented to six Mandarin-speaking, NH adult listeners for identification. Results The acoustic analysis revealed that the children with CIs deviated from the NH controls in the acoustic features for both single vowels and compound vowels. The acoustic deviations were reflected in longer duration, more scattered vowel categories, smaller vowel space area, and distinct formant trajectories in the children with CIs in comparison to NH controls. The vowel intelligibility results showed that the recognition accuracy of the vowels produced by the children with CIs was significantly lower than that of the NH children. The confusion pattern of vowel recognition in the children with CIs generally followed that in the NH children. Conclusion Our data suggested that the prelingually deafened children with CIs, with a relatively long duration of CI experience, still showed measurable acoustic deviations and lower intelligibility in vowel productions in comparison to the NH children.

Is the spontaneous speech of 7-year-old cochlear implanted children as intelligible as that of their normally hearing peers?

OBJECTIVES

Studies on speech intelligibility usually focus on either individual words, sentences or longer sequences of speech. Since these different kinds of speech samples can be judged using different methodologies, a difference in the reported intelligibility scores can either be due to the difference in the type of sample or methodology. The present study compares the speech intelligibility of seven-year-old children with a cochlear implant (CI) with that of their normally hearing (NH) peers. The first aim is to compare the intelligibility of short sentences and longer sequences of speech using the same methodology. Secondly, it has been suggested that i.a. advances in CI technology and changes in candidacy criteria may have had a positive influence on the intelligibility of children with CI. In order to assess this issue, the intelligibility of seven-year-olds implanted ten years apart will be compared.

METHOD

The speech of two cohorts of early implanted children with CI (n = 16) and NH peers (n = 16), matched on several criteria but implanted in different years, was collected. More specifically, short and longer samples were selected from recordings of a wordless picture book retelling. Both types of samples were judged on a visual analogue scale by 105 inexperienced listeners.

RESULTS

The results showed that the intelligibility of children with CI was lower than that of their NH peers. Moreover, longer samples were significantly more intelligible than short samples for both groups. No significant effect was found between the two cohorts of children with CI. However, the intelligibility of three out of four children with CI was found to be on a par with that of their NH peers, indicating a large amount of variability between subjects.

CONCLUSION

Listeners ascribed higher intelligibility to longer samples than to short samples, despite the fact that both types were extracted from the same recordings and listeners followed the same judgement procedure. The amount of context thus facilitated speech decoding. No effect of the calendar year of implantation was found, suggesting that e.g., the evolution in CI technology did not have a significant impact on CI users' intelligibility after six years of device use.

Speech intelligibility and auditory perception of pre-school children with Hearing Aid, cochlear implant and Typical Hearing

Purpose

There is a growing interest in speech intelligibility and auditory perception of deaf children. The aim of the present study was to compare speech intelligibility and auditory perception of pre-school children with Hearing Aid (HA), Cochlear Implant (CI), and Typical Hearing (TH).

Methods

The research design was descriptive-analytic and comparative. The participants comprised 75 male pre-school children aged 4–6 years in the 2017–2018 from Tehran, Iran. The participants were divided into three groups, and each group consisted of 25 children. The first and second groups were respectively selected from pre-school children with HA and CI using the convenience sampling method, while the third group was selected from pre-school children with TH by random sampling method. All children completed Speech Intelligibility Rating and Categories of Auditory Performance Questionnaires.

Results

The findings indicated that the mean scores of speech intelligibility and auditory perception of the group with TH were significantly higher than those of the other groups (P < 0.0001). The mean scores of speech intelligibility in the group with CI did not significantly differ from those of the group with HA (P < 0.38). Also, the mean scores of auditory perception in the group with CI were significantly higher than those of the group with HA (P < 0.002).

Conclusion

The results showed that auditory perception in children with CI was significantly higher than children with HA. This finding highlights the importance of cochlear implantation at a younger age and its significant impact on auditory perception in deaf children.

Acoustic characteristics of Arabic pharyngealized obstruents in children with cochlear implants

Speech production of children with cochlear implants (CIs) is generally characterized by low intelligibility and reduced phoneme accuracy. However, limited research investigated their speech production using acoustic measures. The current study examined voice onset time (VOT) for pharyngealized plosives [t,d], and spectral moments and noise duration for pharyngealized fricatives [s,ð] produced by Arabic speaking children with CIs. Productions from children with CIs were compared with both chronological age-matched and hearing experience-matched normal hearing children. Results showed that children with CIs exhibited difficulty producing distinct VOTs between plosives and produced different spectral patterns of both fricatives relative to both comparison groups; however, they were able to produce an acoustic distinction between both fricatives. Children with CIs produced the fricatives with lower spectral mean and higher skewness and kurtosis. The sources for inter-group differences in the acoustic measures appeared to be due in part to limitations in the quality of auditory input provided by CIs as well as reduced motor experience in speech production. Results suggest that VOT and spectral moments are sensitive to changes in perceived sound quality. Spectral moments analysis appears to give details on subtle aspects of fricative production at the phonetic level beyond that available using perceptual judgments.

Phonological processes in the speech of school-age children with hearing loss: Comparisons with children with normal hearing

PURPOSE

In this descriptive study, phonological processes were examined in the speech of children aged 5;0-7;6 (years; months) with mild to profound hearing loss using hearing aids (HAs) and cochlear implants (CIs), in comparison to their peers. A second aim was to compare phonological processes of HA and CI users.

METHOD

Children with hearing loss (CWHL, N = 25) were compared to children with normal hearing (CWNH, N = 30) with similar age, gender, linguistic, and socioeconomic backgrounds. Speech samples obtained from a list of 88 words, derived from three standardized speech tests, were analyzed using the CASALA (Computer Aided Speech and Language Analysis) program to evaluate participants' phonological systems, based on lax (a process appeared at least twice in the speech of at least two children) and strict (a process appeared at least five times in the speech of at least two children) counting criteria.

RESULTS

Developmental phonological processes were eliminated in the speech of younger and older CWNH while eleven developmental phonological processes persisted in the speech of both age groups of CWHL. CWHL showed a similar trend of age of elimination to CWNH, but at a slower rate. Children with HAs and CIs produced similar phonological processes. Final consonant deletion, weak syllable deletion, backing, and glottal replacement were present in the speech of HA users, affecting their overall speech intelligibility.

CONCLUSIONS

Developmental and non-developmental phonological processes persist in the speech of children with mild to profound hearing loss compared to their peers with typical hearing. The findings indicate that it is important for clinicians to consider phonological assessment in pre-school CWHL and the use of evidence-based speech therapy in order to reduce non-developmental and non-age-appropriate developmental processes, thereby enhancing their speech intelligibility.

The effect of age of cochlear implantation on vocal characteristics in children

Background

Early cochlear implantation aids auditory feedback and supports better communication and self-monitoring of the voice. The objective of this study was to determine whether the age of cochlear implantation has an impact on vocal development in children implanted before age 4.

Method and procedures

The study consisted of 19 participants in total. All implant recipients (experimental group) were 3–5 years post-implantation, including four prelingual (0–2 years) and five perilingual (2–4 years) implant recipients. The control group consisted of 10 children whose hearing was within normal limits between the ages 3–6 years and 10 months, which was compared to the experimental group. Established paediatric norms were used for additional comparison. A questionnaire was used to gather information from each of the participant’s caregivers to determine whether other personal and contextual factors had an impact on voice production. An acoustic analysis was conducted for each participant using the Multi-Dimensional Voice Program of the Computerized Speech Lab.

Results

When the experimental group and the control group were compared, similar results were yielded for fundamental frequency and short-term perturbation (jitter and shimmer). More variability was noted in long-term frequency and amplitude measures, with significantly higher differences, and therefore further outside the norms, in the prelingual group when compared to the perilingual and control groups.

Conclusion

In this study, age of implantation did not impact vocal characteristics. Further research should include larger sample sizes, with participants that are age and gender matched.

Typical consonant cluster acquisition in auditory-verbal children with early-identified severe/profound hearing loss

Early-identified severe/profound hearing loss (HL) following universal newborn hearing screening (UNHS) has been associated with improved speech and language outcomes. However, speech outcome reports have typically been based on broad measures of speech intelligibility and/or singleton consonant accuracy, with little known about production of consonant clusters. Using a prospective design, the range and accuracy of consonant clusters produced by a homogenous cohort of 12 children early-identified with severe/profound HL aged 3- and 4-years were examined. All children demonstrated bilateral aided thresholds within a range of 15-25 dB HL across all frequencies, were optimally amplified with cochlear implants (11/12) or hearing aids (1/12), and attended auditory-verbal (AV) early intervention. Standardized speech and language assessments were administered. Consonant clusters were strategically sampled in single-word and conversational speech contexts. All standard scores for speech, receptive, and expressive language were within normal limits. All children produced consonant clusters commensurate with expectations for typically-developing hearing peers at 3- and 4- years-of-age. Children's production of phonetically complex morphophonemes (final consonant clusters marking grammatical morphemes) was also in keeping with developmental expectations. Factors which contributed to these encouraging outcomes require further investigation.

The conversational skills of school-aged children with cochlear implants

Children with cochlear implants have been shown to have language skills on a par with children with severe hearing losses who have hearing aids. Earlier implants, bilateral implantation, and focused intervention programmes may result in some children with cochlear implants displaying similar language skills to their hearing peers. The development of pragmatic skills is central to communication competence and underpins the development of friendships. Although some studies of pragmatic skills in children with cochlear implants have been reported, most have used a contrived referential communication task rather than free conversation.

METHOD

This study investigated the conversational skills of 20 children with cochlear implants, aged between 9 and 12 years, in free conversation with their hearing peers. The pragmatic skills of these 20 deaf/hearing pairs or dyads were compared with the pragmatic skills of 20 hearing/hearing dyads. Pragmatic skills were analysed in terms of conversational balance, conversational turn types, and conversational maintenance. The impact of the participants' level of speech intelligibility was also investigated.

RESULTS

Children with cochlear implants tend to dominate conversations with their hearing peers. They initiated more topics, took longer turns, asked more questions, and tended to make more personal comments while their hearing friends tended to use more conversational devices and minimal answers. In contrast, pairs of matched hearing children were very balanced in all of these aspects of conversation. Speech intelligibility did not appear to impact consistently on the pragmatic skills of the children with cochlear implants but all children had a relatively high level of speech intelligibility.

DISCUSSION

Rather than being characterized by frequent conversational breakdown as in older studies, children with cochlear implants had a strong grasp of basic conversational rules. They conversed in a similar way to some deaf adults who also have been shown to take control of the conversation. Findings are discussed for their implications for intervention and future research.

Speech perception outcomes after cochlear implantation in prelingually deaf infants: the Western Sicily experience

OBJECTIVES

To describe audiometric characteristics and speech perception performances of prelingually deaf Sicilian children after cochlear implantation; to identify the influence of cochlear implant (CI) user and family's characteristics on speech recognition and intelligibility outcomes.

METHODS

Twenty-eight infants with a congenital or acquired hearing impairment and implanted before the 3rd year of life were studied; all children suffered from bilateral sensorineural hearing loss (SNHL) with evidence of lack of hearing aids benefit and no evidence of intellectual disability. The study of the main characteristics associated with CI user and family's profile was performed with a clinical assessment including pre-implant and post-implant (1, 3, 6, 12 and 18 months) behavioural audiometry (evaluating average threshold for the frequencies 0.5, 1, 2 and 4KHz) and speech recognition tests (IT-MAIS, MUSS, CAP and SIR).

RESULTS

Our cohort was characterized by an early diagnosis of SNHL (5.77 and 12.17 months for congenital and acquired HL respectively), a short length of deafness (average=6.78 months) and an implantation before the 3rd year of life (mean=24.25 months; range from 10 to 36). Analysis of audiometric threshold revealed a significantly improved capacity to detect sounds within the conversational speech spectrum after 12 months from implantation (r=0.99; p<0.001). The main speech recognition test evidenced speech perception and speech intelligibility performances (CAP median value of 3; SIR category=3 in 46.42%) equal to those children with same characteristics reported by literature. With the exception of 'daily CI use' (p<0.001), none of the variables associated with CI user and family's profile resulted significant predictor of speech perception improvement.

CONCLUSIONS

This work demonstrates that all children of our cohort, with an early diagnosis of SNHL and a CI surgery performed before the 3rd year of life, presented a progressive audiometric and speech improvement through the first 12-18 months after cochlear implantation. The study also highlights that, differently from the others variables studied, a continuous CI use influences significantly speech perception and recognition outcomes.

Listen up: children with early identified hearing loss achieve age-appropriate speech/language outcomes by 3 years-of-age

OBJECTIVES

Age-appropriate speech/language outcomes for children with early identified hearing loss are a possibility but not a certainty. Identification of children most likely to achieve optimal outcomes is complicated by the heterogeneity of the children involved in outcome research, who present with a range of malleable (e.g. age of identification and cochlear implantation, type of intervention, communication mode) and non-malleable (e.g. degree of hearing loss) factors. This study considered whether a homogenous cohort of early identified children (≤ 12 months), with all severities of hearing loss and no other concomitant diagnoses could not only significantly outperform a similarly homogenous cohort of children who were later identified (>12 months to <5 years), but also achieve and maintain age-appropriate speech/language outcomes by 3, 4 and 5 years of age.

METHODS

A mixed prospective/retrospective comparative study of a homogenous cohort of 45 early identified (≤ 12 months) and 49 late identified (> 12 months to < 5 years) children with hearing loss was conducted. The children all attended the same oral auditory-verbal early intervention programme. Speech/language assessments standardized on typically developing hearing children were conducted at 3, 4 and 5 years of age.

RESULTS

The early identified children significantly outperformed the late identified at all ages and for all severities of HL. By 3 years of age, 93% of all early identified participants scored within normal limits (WNL) for speech; 90% were WNL for understanding vocabulary; and 95% were WNL for receptive and expressive language. Progress was maintained and improved so that by 5 years of age, 96% were WNL for speech, with 100% WNL for language.

CONCLUSIONS

This study found that most children with all severities of hearing loss and no other concomitant diagnosed condition, who were early diagnosed; received amplification by 3 months; enrolled into AV intervention by 6 months and received a cochlear implant by 18 months if required, were able to "keep up with" rather than "catch up to" their typically hearing peers by 3 years of age on measures of speech and language, including children with profound hearing loss. By 5 years, all children achieved typical language development and 96% typical speech.

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.

Intelligibility of hearing impaired children as judged by their parents: A comparison between children using cochlear implants and children using hearing aids

OBJECTIVES

The aim of this study was to determine the intelligibility of prelingually deaf children with cochlear implants (CI) as judged by their own parents, and to compare these results with prelingually hearing impaired children using hearing aids (HA) and normally hearing (NH) children. The authors hypothesised that subjects using conventional hearing aids would have poorer intelligibility judgements compared to NH and CI children.

METHODOLOGY

This is a comparative study of 24 prelingually deaf CI children (m.a. 8.3 years), 24 prelingually hearing impaired HA children (m.a. 9.0 years) and 25 NH children. Recorded speech samples at word-, sentence- and story-level were perceptually judged by two speech pathologists and the child's main caregiver (the mother in most cases) using a five-point hierarchical scale. In addition, the sample of each child was transcribed by the child's main caregiver. The investigators counted and determined a percentage of words correctly understood.

RESULTS

The judgements of the speech pathologists and the transcriptions of the mothers were not different between the CI and NH children, although the mothers tended to judge their CI child to be less intelligible. The HA children on the other hand, showed a mean intelligibility inferior to NH and CI children, as demonstrated by the judgements of the mothers and speech pathologists as well as by the percentages of correctly identified words by the mothers.

CONCLUSION

The intelligibility of the prelingually deaf CI children is very close to the intelligibility of NH children, while the HA children still show a decreased mean intelligibility.

Single word and sentence intelligibility in children with cochlear implants

This study examined the intelligibility of speech produced by 17 children (aged 4-11 years) with cochlear implants. Stimulus items included sentences from the Beginners' Intelligibility Test (BIT) and words from the Children Speech Intelligibility Measure (CSIM). Naïve listeners responded by writing sentences heard or with two types of responses to the word recordings; open transcription (CSIM-T) and closed set multiple choice (CSIM-MC). Percentage of items understood, averaged across three naïve judges, were compared across the three measures. Additionally, scores were examined for any relationships with chronological age, age of implantation, and amount of implant experience. Strong positive correlations were observed among all three intelligibility tasks. Scores on all three tasks were found to be significantly different from each other. A significant correlation was obtained between intelligibility and amount of implant experience, but not with chronological age or age of implantation. Results suggest that judging the intelligibility of speech produced by children with cochlear implants using both single word and sentence levels would provide a better overall estimate of their intelligibility. The results also emphasize the vital role of auditory input in the development of intelligible speech.