Graeme Clark Collection
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ItemA multiple-channel cochlear implant: an evaluation using nonsense syllables( 1981)A study using nonsense syllables has shown that a multiple-channel cochlear implant with speech processor is effective in providing information about, voicing and manner and to a lesser extent place distinctions. These distinctions supplement lipreading cues. Furthermore, the average percentage improvements in overall identification scores for multiple-channel electrical stimulation and lipreading compared to lipreading alone were 71% for a laboratory-based speech processor and 122 % for a wearable unit.
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ItemSpeech processing for a multiple-electrode cochlear implant hearing prosthesis( 1980)Abstract not available due to copyright.
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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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ItemRecent developments with the Nucleus 22-electrode cochlear implant: a new two formant speech coding strategy and its performance in background noise( 1987)A clinical evaluation of speech processing strategies for the Nucleus 22-electrode cochlear implant showed improvements in understanding speech using the new F0F1F2 speech coding strategy instead of the F0F2 strategy. Significant improvement in closed-set speech recognition in the presence of background noise was an additional advantage of the new speech processing strategy.
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ItemSpeech perception using a two-formant 22-electrode cochlear prosthesis in quiet and in noise( 1987)A new speech-processing strategy has been developed for the Cochlear Pty. Ltd. 22-electrode cochlear prosthesis which codes an estimate of the first formant frequency in addition to the amplitude. voice pitch and second formant frequencies. Two groups of cochlear implant patients were tested 3 months after implant surgery, one group (n= 13) having used the old (F0F2) processing strategy and the other (n=9) having used the new (F0FIF2) strategy. All patients underwent similar postoperative training programs. Results indicated significantly improved speech recognition for the F0FIF2 group particularly on open set tests with audition alone. Additional testing with a smaller group of patients was carried out with competing noise (speech babble). Results for a closed set spondee test showed that patient performance was significantly degraded at a signal-to-noise ratio of 10 dB when using the F0F2 strategy, but was not significantly affected with the F0FIF2 strategy.
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ItemEvaluation of a two-formant speech-processing strategy for a multichannel cochlear prosthesis( 1987)Initial results with the two-formant speech-processing strategy (F0FIF2) confirm the advantage of a multichannel cochlear prosthesis capable of stimulating at different sites within the cochlea. The successful presentation of two spectral components by varying the place of stimulation leads to the possibility of presenting further spectral information in this manner. Because virtually all multichannel implant patients demonstrate good "place" (electrode site) discrimination, these more refined coding strategies should lead to benefits for the majority of implantees. Already, with the F0FIF2 strategy, we have a system that appears to provide some effective auditory-alone communication ability for the average patient.
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ItemA multiple-electrode intracochlear implant for children( 1987)A multiple-electrode intracochlear implant that provides 21 stimulus channels has been designed for use in young children. It is smaller than the adult version and has magnets to facilitate the attachment of the headset. It has been implanted in two children aged 5 and 10 years. The two children both lost hearing in their third year, when they were still learning language. Following implantation, it was possible to determine threshold and comfortable listening levels for each electrode pair. This was facilitated in the younger child by prior training in scaling visual and electrotactile stimuli. Both children are regular users of the implant, and a training and assessment program has been commenced.
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ItemAcoustic parameters measured by a formant-estimating speech processor for a multiple-channel cochlear implant( 1987)Abstract not available due to copyright.
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ItemVowel and consonant recognition of cochlear implant patients using formant-estimating speech processors( 1987)Abstract not available due to copyright.
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ItemA formant-estimating speech processor for cochlear implant patients( 1987)A simple formant-estimating speech processor has been developed to make use of the “hearing” produced by electrical stimulation of the auditory nerve with a multiple-channel cochlear implant. Thirteen implant patients were trained and evaluated with a processor that presented the second formant frequency, fundamental frequency, and amplitude envelope of the speech (F0F2). Nine patients were trained and evaluated with a processor that presented the first and second formant frequencies, fundamental frequency, and first and second formant amplitudes (F0F1F2). The most common use of the speech processor was in conjunction with lipreading, so the patients were trained in lipreading plus hearing, as well as hearing alone. The F0F1F2 group performed significantly better in discrimination tasks and word and sentence recognition through hearing alone. The F0F1F2 group also showed a significantly greater improvement when hearing and lipreading was compared with lipreading alone in a speech tracking task. A study of spondee recognition in noise with hearing alone indicated that the added first formant information produced an improvement that was equivalent to a 5 dB increase in the signal-to-noise ratio.