Graeme Clark Collection
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ItemSynthetic vowel studies on cochlear implant patients( 1988)Abstract not available due to copyright.
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ItemPerceptual studies on cochlear implant patients with early onset of profound hearing impairment prior to normal development of auditory, speech, and language skills( 1988)Abstract not available due to copyright.
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ItemPreliminary evaluation of a wearable multichannel electrotactile speech processor [Abstract]( 1988)Speech discrimination testing, using both open-and closed-set materials was carried out with four severely-to-profoundly hearing impaired adults. and seven normally hearing subjects, to assess performance of a wearable eight-channel electrotactile aid (Tickle Talker). The device consisted of a handset composed of nine electrodes, a stimulator-unit, and a speech processor and input microphone. Eight small electrodes were located over the digital nerve bundles on each side of the four fingers of one hand, and a larger common electrode was placed on the wrist. Subjects perceived eight separate channels of information, each corresponding to a stimulus on one side of one finger. The speech processor provided estimates of second formant frequency, fundamental frequency and amplitude of the speech waveform. These features were coded as electrode position, pulse rate and pulse width respectively. This processing strategy (FOF2AO) is similar to that used in an earlier model of the Cochlear Pty. Ltd. cochlear implant.
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ItemPreliminary evaluation of a multichannel electrotactile speech processor( 1988)Abstract not available due to copyright.
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ItemThe histopathology of the human temporal bone and auditory central nervous system following cochlear implantation in a patient: correlation with psychophysics and speech perception results( 1988)Cochlear implantation has become a recognised surgical procedure for the management of a profound-total hearing loss, especially in patients who have previously had hearing before going deaf (postlingual deafness). Nevertheless, it is important for progress in the field that patients who have had a cochlear implant, bequeath their temporal bones for research. This will then make it possible to further assess the safety of the procedure, and the factors that are important for its effectiveness. Biological safety has been assessed in a number of studies on animals, in particular, the biocompatibility of the materials used (1,2), the histopathological effects of long-term implantation on the cochlea (3, 4, 5, 6, 7, 8), and the effects of chronic electrical stimulation on the viability of spiral ganglion cells (9, 10, 11, 12). In studying the temporal bones of deceased cochlear implant patients it is possible to help establish that the animal experimental results are applicable to Man. Surgical trauma has been most frequently evaluated by inserting electrodes into cadaver temporal bones. It is important, however, to examine bones that have been previously implanted surgically to ensure that the cadaver findings are applicable to operations on patients. The effectiveness of cochlear implantation can be studied by correlating the histopathological findings, the dendrite and spiral ganglion cell densities, in particular, with the psychophysical and speech perception results. Other benefits also accrue, for example, establishing the accuracy of preoperative X-rays and electrical stimulation of the promontory in predicting cochlear pathology and spiral ganglion cell numbers. For the above reasons it has been especially interesting to examine both the temporal bones and central nervous system from one of our patients (patient 13) who participated in the initial clinical trial of the Cochlear Proprietary Limited (a member of the Nucleus group) multiple-electrode cochlear prosthesis, and who died due to a myocardial infarction following coronary bypass surgery.
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ItemThe University of Melbourne/Nucleus cochlear prosthesis( 1988)This is a review of research to develop the University of Melbourne/Nucleus cochlear prosthesis for patients with a profound-total hearing loss. A more complete review can be obtained in Clark et al. A prototype receiver-stimulator and multiple-electrode array developed at the University of Melbourne was first implanted in a postlingually deaf adult patient with a profound-total hearing loss on 1 August 1978. A speech processing strategy which could help this patient understand running speech, especially when combined with lipreading was developed in 1978 following initial psychophysical studies. A prototype wearable speech processor was fabricated in 1979, that could provide significant help for the first two patients in understanding running speech when used in combination with lipreading compared with lipreading alone, and it also enabled them to understand some running speech when using electrical stimulation alone. An implantable receiver-stimulator and wearable speech processor embodying the principles of the prototype devices were then produced for clinical trial by the Australian biomedical firm, Nucleus Ltd, and its subsidiaries, Cochlear Pty Ltd and Cochlear Corporation. This cochlear implant was initially clinically trialled on six patients at The Royal Victorian Eye & Ear Hospital in 1982, and shown to give similar results to those obtained with the prototype device. In view of these findings a clinical trial was carried out for a Premarket Approval Application to the US Food and Drug Administration (FDA), and extended to a number of centres in the US, Canada, and West Germany. This clinical trial confirmed that patients could understand running speech when electrical stimulation was combined with lipreading, and that some patients could also understand running speech when using electrical stimulation alone. Today, more than 600 patients world-wide are using cochlear implants developed from the research described in this paper.
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ItemUnderlying structure of auditory-visual consonant perception by hearing-impaired children and the influences of syllabic compression( 1988)The identification of consonants in /a/-C-/a/ nonsense syllables, using a fourteen-alternative forced-choice procedure, was examined in 4 profoundly hearing-impaired children under five conditions: audition alone using hearing aids in free-field (A), vision alone (V), auditory-visual using hearing aids in free-field (AV1), auditory-visual with linear amplification (AV2), and auditory-visual with syllabic compression (AV3). In the AV2 and AV3 conditions, acoustic signals were binaurally presented by magnetic or acoustic coupling to the subjects' hearing aids. The syllabic compressor had a compression ratio of 10:1, and attack and release times were 1.2 ms and 60 ms. The confusion matrices were subjected to two analysis methods: hierarchical clustering and information transmission analysis using articulatory features. The same general conclusions were drawn on the basis of results obtained from either analysis method. The results indicated better performance in the V condition than in the A condition. In the three AV conditions, the subjects predominately combined the acoustic parameter of voicing with the visual signal. No consistent differences were recorded across the three AV conditions. Syllabic compression did not, therefore, appear to have a significant influence on AV perception for these children. A high degree of subject variability was recorded for the A and three AV conditions, but not for the V condition.
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ItemPhonemic information transmitted by a multichannel electrotactile speech processor( 1988)A wearable electrotactile speech processor was evaluated in a study with seven normally hearing and four hearing-impaired subjects. The processor estimated the fundamental frequency, the second-formant frequency, and amplitude of the acoustic speech signal. These parameters were presented as a pattern of electrical pulses applied to eight electrodes positioned over the digital nerve bundles on one hand. The device was shown to provide useful information for the recognition of phonemes in closed sets of words using tactile information alone. The device also supplemented lipreading to improve the recognition of open-set words. The recognition of duration and first-and second-formant frequencies of vowels and the recognition of voicing and manner of consonants were improved over recognition with lipreading alone. Recognition of final consonants was improved more than recognition of initial consonants. These results indicate that the device may be useful to both severely and profoundly hearing-impaired people.
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ItemSpeech perception with cochlear implants and tactile aids [Abstract]( 1988)Abstract not available due to copyright.
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ItemEvaluation of training strategies with an electrotactile speech processor [Abstract]( 1988)During 1986, seven normally-hearing subjects were trained in the use of an electrotactile speech processor ("Tickle Talker"). Two training methods were used: (a) a combined strategy. in which a variety of training materials ranging from analytic to synthetic level were employed; and (b) a synthetic alone training strategy, in which only synthetic level training materials were used. All seven subjects received 70 hours of training, 35 hours in each training strategy. Subjects were evaluated in the tactile-lipreading (TL) and lipreading alone (L) conditions at: (I) 0 hours training; (2) 35 hours training; and (3) after 70 hours of training. An evaluation test battery was constructed which contained both closed-set and open-set materials. Results indicated differences in performance on the evaluation tests which were dependent upon the training strategy. The differences in performance were greater in some evaluation tests than others. Subsequently; seven severe-profoundly hearing-impaired children (aged 7-11) have been fitted with the Tickle Talker and are presently participating in an ongoing training programme. Evaluation of their performance will help to assess the suitability of the device for young children.