Graeme Clark Collection
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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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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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ItemThe effect of language knowledge on speech perception in children with impaired hearing( 1996)Open-set words and sentences were used to assess auditory speech perception of three hearing-impaired children aged 9 to 15 years using the Nucleus 22channel cochlear implant. Vocabulary and syntax used in the tests were assessed following the initial perception tests. Remediation was given in specific vocabulary and syntactic areas, chosen separately for each child, and the children were reassessed. Two children showed a significant post-remediation improvement in their overall scores on the syntactic test and both perception measures. The third child who was older, had the best language knowledge and the lowest auditory speech perception scores, showed no significant change on any of the measures. Language remediation in specific areas of weakness may be the quickest way to enhance speech perception for some children with impaired hearing in this age range.
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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.
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ItemUsing an automatic word-tagger to analyse the spoken language of children with impaired hearing( 1994)The grammatical analysis and description of spoken language of children with impaired hearing is time-consuming, but has important implications for their habilitation and educational management. Word-tagging programs have achieved high levels of accuracy with text and adult spoken language. This paper investigates the accuracy of one automatic word tagger (AUTASYS 3.0 developed for the International Corpus of English project, ICE) on a small corpus of spoken language samples from children using a cochlear implant. The accuracy of the tagging and the usefulness of the results in comparison with more conventional analyses are discussed.
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ItemFricative perception by cochlear implant users( 1992)Three implant users were tested with 45 syllables consisting of[v, f, �, ?, z, s, ?, ?, d?, t ?, ?, , d, n, 1] before the vowels [I ,a,u] with three wearable speech processors. The WSP3 processor coded first and second formant frequencies and amplitudes. The MSP1 processor used a similar scheme with improved measurement and coding of the formants. The MSP2 processor added amplitude information from three higher frequency bands. Average scores were 42% for WSP3, 54% for MSP1, and 57% for MSP2. Perception of voicing, manner, and place of articulation of the consonants was significantly greater for the MSP processors than the WSP3 processor. Place perception was slightly higher for MSP2 than MSP1. The listeners used three perceptual dimensions which were highly correlated with the frequencies and amplitudes of peaks in the low frequency region of the frication spectrum, amplitudes of high frequency peaks, and duration of the frication noise.
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ItemSpeech perception, production and language results in a group of children using the 22-electrode cochlear implant( 1989)Paper presented at the 118th Meeting of the Acoustical Society of America
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ItemSpeech processing strategies in an electrotactile aid for hearing-impaired adults and children(Australian Speech Science and Technology Association, 1990)An electrotactile speech processor (Tickle Talker) for hearing-impaired children and adults has been developed and tested. Estimates of second format frequency, fundamental frequency and speech amplitude are extracted from the speech input, electrically encoded and presented to the user through eight electrodes located over the digital nerve bundles on the fingers of the non-dominant hand. Clinical results with children and adults confirm that tactually-encoded speech features can be recognized, and combined with input from vision or residual audition to improve recognition of words in isolation or in sentences. Psychophysical testing suggests that alternative encoding strategies using multiple-electrode stimuli are feasible. Preliminary results comparing encoding of consonant voiced/voiceless contrasts with new encoding schemes are discussed.
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ItemCombining tactile, auditory and visual information for speech perception( 1988)Four normally hearing subjects were trained and tested with all combinations of a highly degraded auditory input, a visual input via lipreading, and a tactile input using a multichannel electrotactile speech processor. When the visual input was added to any combination of other inputs, a significant improvement occurred for every test. Similarly, the auditory input produced a significant improvement for all tests except closed-set vowel recognition. The tactile input produced scores that were significantly greater than chance in isolation, but combined less effectively with the other modalities. The less effective combination might be due to lack of training with the tactile input, or to more fundamental limitations in the processing of multimodal stimuli.