Graeme Clark Collection
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ItemAdvances with the 22-channel cochlear implant(Kugler & Ghedini, 1988)The Nucleus 22 Channel Cochlear Implant was developed on the basis of work at the University of Melbourne. Between 1967 and 1978, there was extensive research with animals and human temporal bones, especially regarding safety, psychophysics, histopathology and surgical approaches. As a result of this work, it was decided to develop a multi-channel intracochlear implant. The 22 channel implant has been used in more than 500 patients world-wide but there were many steps on the road to this success. Today, over one third of the post-lingually profound, deaf adults implanted with this device have significant speech understanding without lipreading.
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ItemSurgery for multielectrode cochlear implants( 1987)For the surgery of the NUCLEUS Cochlear Implant (CI) in general anaesthesia we use a skin cut beginning at the bottom of the entrance to the outer ear canal, following the posterior circumference to a point nearly 12 o'clock. From here the incision runs superiorly to the tragus until two or three centimetres above the pinna base and in a wide smooth circle in direction to the occiput. The wide circle is necessary to get a distance of about 2 cm away from the package and also to guarantee the blood supply by the occipital artery and by the postauricular artery as well.
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ItemSignal processing in quiet and noise( 1987)It has been shown that many profoundly deaf patients using multichannel cochlear implants are able to understand significant amounts of conversational speech using the prosthesis without the aid of lipreading. These results are usually obtained under ideal acoustic conditions but, unfortunately, the environments in which the prostheses are most often used are rarely perfect. Some form of competing signal is always present in the urban setting, from other conversations, radio and television, appliances, traffic noise and so on. As might be expected, implant users in general find background noise to be the largest detrimental factor in their understanding of speech, both with and without the aid of lipreading. Recently, some assessment of implant patient performance with competing noise has been attempted using a four-alternative forced-choice spondee test (1) at Iowa University. Similar testing has been carried out at the University of Melbourne with a group of patients using the Nucleus multichannel cochlear prosthesis. This study formed part of an assessment of a two formant (F0/FI/F2) speech coding strategy (2). Results suggested that the new scheme provided improved speech recognition both in quiet and with competing noise. This paper reports on some more detailed investigations into the effects of background noise on speech recognition for multichannel cochlear implant users.
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ItemThe histopathology of the human temporal bone following cochlear implantation in a patient: a summary( 1987)The macroscopic and microscopic evaluation of the implanted and unimplanted temporal bones in a patient who had a cochlear prosthesis for 27 months prior to his death from cardiac disease has shown that the device is biocompatible, and does not lead to any significant adverse effects. The cause of deafness was meningitis.
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ItemA formant-estimating speech processor for cochlear implant patients(Speech Science and Technology Conference, 1986)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. Nine patients were trained and evaluated with a processor that presented the first formant frequency and amplitude as well. The second group performed significantly better in discrimination tasks and word and sentence recognition through hearing alone. The second group also showed a significantly greater improvement when hearing and lipreading was compared with lipreading alone in a speech tracking task.
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ItemA model of auditory-visual speech perception(Speech Science and Technology Conference, 1986)A mathematical model relating the probabilities of correctly recognizing speech features, phonemes, and words was tested using data from the clinical trial of a multiple-channel cochlear implant. A monosyllabic word test was presented to the patients in the conditions hearing alone (H), lipreading alone (L), and hearing plus lipreading (HL). The model described the data quite well in each condition. The model was extended to predict the HL scores from the feature recognition probabilities in the H and L conditions. The model may be useful for the evaluation of automatic speech recognition devices as well as hearing impaired people.