ObjectivesCochlear implantees have improved speech production skills compared with those using hearing aids, as reflected in their acoustic measures. When compared to normal hearing controls, implanted children had fronted vowel space and their /s/ and /∫/ noise frequencies overlapped. Acoustic analysis of speech provides an objective index of perceived differences in speech production which can be precursory in planning therapy. The objective of this study was to compare acoustic characteristics of speech in cochlear implantees with those of normal hearing age matched peers to understand implications.MethodsGroup 1 consisted of 15 children with prelingual bilateral severe-profound hearing loss (age, 5-11 years; implanted between 4-10 years). Prior to an implant behind the ear, hearing aids were used; prior & post implantation subjects received at least 1 year of aural intervention. Group 2 consisted of 15 normal hearing age matched peers. Sustained productions of vowels and words with selected consonants were recorded. Using Praat software for acoustic analysis, digitized speech tokens were measured for F1, F2, and F3 of vowels; centre frequency (Hz) and energy concentration (dB) in burst; voice onset time (VOT in ms) for stops; centre frequency (Hz) of noise in /s/; rise time (ms) for affricates. A t-test was used to find significant differences between groups.ResultsSignificant differences were found in VOT for /b/, F1 and F2 of /e/, and F3 of /u/. No significant differences were found for centre frequency of burst, energy concentration for stops, centre frequency of noise in /s/, or rise time for affricates. These findings suggest that auditory feedback provided by cochlear implants enable subjects to monitor production of speech sounds.ConclusionAcoustic analysis of speech is an essential method for discerning characteristics which have or have not been improved by cochlear implantation and thus for planning intervention.
A systematic approach in the form of a kit comprising of audio cassettes and CD-ROMs is now available in Hindi and Marathi for use at home for professionals and parents of children with hearing impairment.
The present study aims to provide a qualitative description and comparison of speech perception performance using model based tests like multisyllabic lexical neighborhood test (MLNT) and lexical neighborhood test (LNT), in early and late implanted (prelingual) hearing impaired children using cochlear implants. The subjects comprised of cochlear implantees; Group I (early implantees)-n = 15, 3-6 years of age; mean age at implantation-3 years. Group II (late implantees)-n = 15, 7-13 years of age; mean age at implantation-5 years. The tests were presented in a sound treated room at 70 dBSPL. The children were instructed to repeat the words on hearing them. Responses were scored as percentage of words correctly repeated. Their means were computed. The late implantees achieved higher scores for words on MLNT than those on LNT. This may imply that late implantees are making use of length cues in order to aid them in speech perception. The major phonological process used by early implantees was deletion and by the late implantees was substitution. One needs to wait until the child achieves a score of 20 % on LNT before assessing other aspects of his/her speech perception abilities. There appears to be a need to use speech perception tests which are based on theoretical empirical models, in order to enable us to give a descriptive analysis of post implant speech perception performance.
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