Graeme Clark Collection
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ItemAdults with a severe-to-profound hearing impairment: investigating the effects of linguistic context on speech perception( 1998)Linguistic context is known to influence speech perception abilities in adults with normal hearing. Recent reports question the importance of context for adults with a severe-to-profound hearing impairment. The severe reduction and distortion in acoustic input may result in the listener perceiving insufficient acoustic-phonetic cues to allow access to higher level linguistic processing. To investigate this further, a detailed study of the speech recognition of adults with a severe-to-profound hearing impairment (N=34) was undertaken. A series of aided speech recognition tasks, sequentially examined the different levels of processing in the speech perception chain. The investigation concluded that the effects of severe-to-profound hearing impairment did not reduce the listener's ability to take advantage of contextual cues. There was, however, wide variability between participants in the utilisation of contextual processing. This indicates that to estimate "real-life" speech perception skills, an evaluation of contextual processing ability is required.
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ItemSpeech perception and spoken language in children with impaired hearing( 1998)Fifty seven children with impaired hearing aged 4-12 years were evaluated with speech perception and language measures as the first stage of a longitudinal study. The Clinical Evaluation of Language Fundamentals (CELF) and Peabody Picture Vocabulary Test (PPVT) were used to evaluate the children's spoken language. Regression analyses indicated that scores on both tests were significantly correlated with chronological age, but delayed relative to children with normal hearing. Performance increased at 45% of the rate expected for children with normal hearing for the CELF, and 62% for the PPVT. Perception scores were not significantly correlated with chronological age, but were highly correlated with results on the PPVT and CELF. The data suggest a complex relationship whereby hearing impairment reduces speech perception, which slows language development, which has a further adverse effect on speech perception.
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ItemThe relationship between aetiology of hearing loss and outcome following cochlear implantation in a paediatric population(Monduzzi Editore, 1997)Eighty-eight children who underwent cochlear implantation at the University of Melbourne Cochlear Implant Clinic are reviewed. The aetiology of the hearing loss is classified and is compared to their best level of speech perception performance. The group whose hearing loss was not congenital in origin performed better than those who were congenital in origin. Of those whose hearing loss was congenital in nature those with rubella appeared to perform best.
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ItemSpeech cues for cochlear implantees: spectral discrimination(Monduzzi Editore, 1997)The relationship between the ability of cochlear implantees to perceive speech and their ability to discriminate between stimulation on adjacent electrodes was investigated. Speech perception ability was assessed with monosyllabic words in 8 users Nucleus cochlear prosthesis. The ability of these subjects to discriminate between stimulation on adjacent electrodes, in of random loudness differences between electrodes was determined. Results were averaged in the apical, mid and basal regions of the cochlea. Regression analysis showed that speech perception ability and electrode discrimination ability were correlated in the apical to mid region of the cochlea. but the two factors were not correlated in the basal region. Therefore, these results suggest that implantees require the ability to discriminate between stimulation on adjacent electrodes in the apical to mid region of the cochlea in order to achieve high speech perception scores.
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ItemSpeech perception of hearing aid users versus cochlear implantees(Monduzzi Editore, 1997)Recent improvements in speech recognition abilities for profoundly deaf cochlear implantees suggests that some adults with a severe hearing impairment might benefit from a cochlear implant. Unfortunately, no studies have directly compared the speech perception abilities of the severely hearing impaired with those of cochlear implant users. An investigation of the speech perception performance of people with a severe hearing loss, who use hearing aids, was conducted in the Department of Otolaryngology at The University of Melbourne. Each participant (n=35) took part in a series of speech perception tests which included 11 vowel recognition tests, CNC words, CUNY sentences, and the Connected Speech Test. The results from these severely hearing impaired persons were compared to results from cochlear implant users. The group of severely hearing impaired adults performed better on tests of vowel and word perception but poorer on tests of open set sentence perception in comparison to a group of cochlear implant users.
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ItemRehabilitation strategies for adult cochlear implant users(Monduzzi Editore, 1997)This paper summarizes open-set speech perception results using audition alone for a large group of adult Nucleus cochlear implant users in Melbourne. The results show wide variation in performance but significant improvement over the years from 1982 to 1995. Analysis of these results shows that speech processor developments have made the major contribution to this improvement over this time. Recent results for patients using the SPECTRA-SPEAK processor show !hat most subjects obtain good speech perception within six months of implantation and the need for intensive auditory training is minimal for many of these patients. Postoperative care should encourage consistent device use by providing opportunities for success and providing long term technical support for implant users. In some cases, including elderly patients, those with long term profound deafness, and those with special needs, there will still be a need for additional rehabilitation and auditory training support.
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ItemFactors affecting outcomes in children with cochlear implants(Monduzzi Editore, 1997)Open-set speech perception tests were completed for a group of 52 children and adolescents who were long-term users of the Nucleus multiple channel cochlear prosthesis. Results showed mean scores for the group of 32.4% for open-set BKE sentences and 48.1% for phonemes in open-set monosyllabic words. Over 80% of the group performed significantly on these tas1cs. Age at implantation was identified as a significant factor affecting speech perception performance with improved scores for children implanted early. This factor was evident in the results at least down to the age of three years. Duration.. of profound hearing loss, progressive hearing loss, educational program and preoperative residual hearing were also identified as significant factors that may affect speech perception performance.
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ItemChanges in synthetic and natural vowel perception after specific training for congenitally deafened patients using a multichannel cochlear implant(Monduzzi Editore, 1997)The study investigated whether congenitally deafened patients using the 22-e1ectrode cochlear implant who show limited speech perception ability, could improve their ability to use place-coded vowel formant information after specific training. The relationship between electrode difference limens and synthetic vowel recognition also investigated. A heterogeneity of findings characterized the patients. Significant improvements on several assessments of synthetic vowel perception occurred after 10 training sessions for 2 of the patients and gains were consistent with their electrode discrimination ability. There were minimal gains for the remaining patients. A poorer apical electrode difference limen could partly explain the relatively low scores pre-and post-training for one of these patients.
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ItemSpeech perception in implanted children: effects of speech processing strategy and residual hearing(Mendoza Editor, 1997)The ability of implanted children to adapt to different speech processing strategies has been demonstrated for the Nucleus implant system. Children previously experienced with the Multipeak speech processing strategy. were able to gain significant improvements in consonant, word and sentence perception using the Speak speech processing strategy. suggesting some degree of neural plasticity in neural-auditory coding. Of 192 implanted children with different degrees of preoperative residual hearing, 65% were found to obtain significant scores on open-set speech materials using electrical stimulation alone. Those children with more residual hearing had a greater probability of achieving open-set understanding and at a minimum level, perceived high frequency consonant information which would not have been available through conventional hearing aids.
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ItemPitch and vowel perception in cochlear implant users( 1994)Two methods of determining the pitch or timbre of electrical stimuli in comparison with acoustic stimuli are described. In the first experiment, the pitch of pure tones and electrical stimuli were compared directly by implant users who have residual hearing in the non-implanted ear. This resulted in a relationship between frequency in the non-implanted ear and position of the best-matched electrode in the implanted ear. In the second experiment, one- and two-formant synthetic vowels, with formant frequencies covering the range from 200 to 4000 Hz, were presented to the same implant users through their implant or through their hearing aid. The listeners categorised each stimulus according to the closest vowel from a set of eleven possibilities, and a vowel centre was calculated for each response category for each ear. Assuming that stimuli at the vowel centres in each ear sound alike, a second relationship between frequency and electrode position was derived. Both experiments showed that electrically-evoked pitch is much lower than that produced by pure tones at the corresponding cochlear location in normally-hearing listeners. This helps to explain why cochlear implants with electrode arrays that rarely extend beyond the basal turn of the cochlea have achieved high levels of speech recognition in postlinguistically deafened adults without major retraining or adaptation by the users. The techniques described also have potential for optimising speech recognition for individual implant users.