Acoustic analysis of the speech of children with cochlear implants: A longitudinal study

Abstract

The aim of the study was to analyse the speech of the children with cochlear implants, and compare it with the speech of hearing controls. We focused on three categories of Croatian sounds: vowels (F1 and F2 frequencies), fricatives (noise frequencies of /s/ and /S/ ), and affricates (total duration and the pattern of stop-fricative components in /ts/ and /tS/ ). Eighteen implanted children, aged between 9;5 and 15;2 years participated in the study. All had been profoundly hearing impaired before implantation. Three recordings per child were made over a 20-month period. The hearing controls were matched for age and sex. Implanted children had a smaller and fronted vowel space, their /s/ and /S/ noise frequencies overlapped, affricates were longer, with a high proportion of incorrect productions and substitutions. With time, there was a small but steady overall improvement in all categories. Early intervention (rehabilitation and implantation) are crucial for good speech acquisition.

Production of contrast between sibilant fricatives by children with cochlear implants

“…The spectral analysis revealed that the children with CIs produced less contrast between /s/ and /$/ than either group of children with NH. This result is consistent with the findings of other studies (Uchanski and Geers, 2003;Liker et al, 2007;Mildner and Liker, 2008), but shows in addition, that children with CIs produced reduced contrast between /s/ and /$/ even for correct productions. This finding indicates that while productions of these sounds by a child with CIs may be perceived as accurate, they likely differ from the productions of children with NH at a subphonemic level.…”

“…The difference in the effect of age on spectral peaks of productions of /s/ and /$/ is consistent with results of Fox and Nissen (2005) who found that over a much larger age range, age explained more of the variability in spectral peak locations of /$/ than of /s/. Uchanski and Geers (2003) and Liker et al (2007) similarly noted that children with CIs produced reduced contrast between /s/ and /$/ due to the production of /s/ at lower frequencies. There are different possible explanations for this finding.…”

“…Studies have shown that children who use CIs produce less acoustic contrast than children with NH when attempting to produce /s/ and /$/ (Uchanski and Geers, 2003;Mildner and Liker, 2008;Liker et al, 2007). In these studies, all productions of target /s/ and /$/ were included in the acoustic analyses as long as the attempts were fricatives.…”

A Comparison of Vowel Productions in Prelingually Deaf Children Using Cochlear Implants, Severe Hearing-Impaired Children Using Conventional Hearing Aids and Normal-Hearing Children

“…Yet, children with CI experience show vowel features closer to normal values. Uchanski and Geers [14] [16] , the mean F 1 [a] of the CI children was significantly lower in comparison with NH controls at 2 of the 3 test moments, indicating reduced movements of the jaw, resulting in a smaller vowel space. The CI children also showed fronted vowel space due to consistently higher F 2 frequencies in comparison with the NH controls.…”

“…The F 2 frequencies were higher for the back vowels, indicating that the vowel space in the CI children is, on average, smaller in comparison with the controls. Liker et al [16] explained the fronting of the vowel space by the tendency of therapists, family and the children themselves to move the articulation to where it is more visible. HocevarBoltezar et al [17] found a decrease in F 1 of the Slovenian vowels [u] and [i] in prelingually deaf children 6 months after implantation.…”