Graeme Clark Collection
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ItemThe development of the Melbourne/Cochlear multiple-channel cochlear implant for profoundly deaf children( 1992)In 1978-79, a speech processing strategy which extracted the voicing (FO) and second formant (F2) frequencies and presented these as rate and place of stimulation respectively to residual auditory nerve fibres was developed for the University of Melbourne's prototype multiple-channel receiver-stimulator (Clark et aI1977, Clark et a11978, Tong et aI1980). This speech processing strategy was shown to provide post linguistically deaf adults with some open-set speech comprehension using electrical stimulation alone, and considerable help when used in combination with lipreading (Clark et al 1981).
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ItemSpeech perception, production and language results in a group of children using the 22-electrode cochlear implant( 1992)Five children out of a group of nine (aged 5.5 to 19.9 years) implanted with the 22-electrode cochlear implant (Cochlear Ply. Ltd.) have achieved substantial scores on open-set speech tests using hearing without lipreading. Phoneme scores for monosyllabic words ranged from 40% to 72%. Word scores in sentences ranged from 26% to 74%. Four of these five children were implanted during preadolescence. The fifth child, who had a progressive loss and was implanted during adolescence after a short period of very profound deafness, scored highest on all speech perception tests. The remaining four children who did not demonstrate open-set recognition were implanted during adolescence after a long duration of profound deafness. Post-operative performance on closed-set speech perception tests was better than pre-operative performance for all children. Improvements in speech and language assessments were also noted. These improvements tended to be greater for the younger children. The results are discussed with reference to variables which may contribute to successful implant use: such as age at onset, duration of profound hearing loss, age at implantation, aetiology, educational program, and the type of training provided.
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ItemThe effects of auditory feedback from the nucleus cochlear implant on the vowel formant frequencies produced by children and adults( 1993)Cochlear implants provide an auditory signal with which profoundly deaf users may monitor their own speech production. The vowel production of two adults and three children who used the Nucleus multiple-electrode cochlear implant was examined to assess the effect of altered auditory feedback. Productions of words were recorded under conditions where the talkers received auditory feedback (speech processor turned on) and where no auditory feedback was provided (speech processor turned off). Data were collected over 3 days at weekly intervals. First and second formant frequencies were measured and the data were analysed to assess significant differences between auditory feedback conditions, vowel context, and data collection points. Overall, the results varied across talkers, across the data collection days, and depended on the consonant environment of the vowel. However, two effects of auditory feedback were noted. First, there was a generalized shift in first formant frequencies between the processor on and processor off conditions across three of the five subjects, but the shift differed in direction for each subject. Second, for three of the five talkers, the two front vowels /ε/ and /I/ were more neutralised in the absence of auditory feedback. However, this effect was less pronounced than that noted by previous studies.
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ItemCochlear implants in children, adolescents, and prelinguistically deafened adults: speech perception( 1992)A group of 10 children, adolescents, and prelinguistically deafened adults were implanted with the 22-electrode cochlear implant (Cochlear Ply Ltd) at the University of Melbourne Cochlear Implant Clinic and have used the prosthesis for periods from 12 to 65 months. Postoperative performance on the majority of closed-set speech perception tests was significantly greater than chance, and significantly better than preoperative performance for all of the patients. Five of the children have achieved substantial scores on open-set speech tests using hearing without lipreading. Phoneme scores in monosyllabic words ranged from 30% to 72%; word scores in sentences ranged from 26% to 74%. Four of these 5 children were implanted during preadolescence (aged 5:5 to 10:2 years) and the fifth, who had a progressive loss, was implanted during adolescence (aged 14:8 years). The duration of profound deafness before implantation varied from 2 to 8 years. Improvements were also noted over postoperative data collection times for the younger children. The remaining 5 patients who did not demonstrate open-set recognition were implanted after a longer duration of profound deafness (aged 13:11to 20:1 years). The results are discussed with reference to variables that may affect implant performance, such as age at onset of loss, duration of profound loss, age at implantation, and duration of implantation. They are compared with results for similar groups of children using hearing aids and cochlear implants.