Graeme Clark Collection
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ItemA multi-channel hearing prosthesis for profound-to-total hearing loss( 1984)A multi-channel cochlear implant hearing prosthesis providing 22 separate channels of stimulation has been developed. The electronics for the implantable receiver-stimulator have been incorporated on a single chip, using digital circuits and employing CMOS technology. The chip is enclosed in a titanium capsule with platinum/ceramic electrode feed-throughs. A pocket-sized speech processor and directional microphone extract the following speech parameters: signal amplitude, fundamental frequency and formant frequency. The fundamental frequency is coded as electric pulse rate, and formant frequency by electrode position. The speech processor has been realized using hybrid circuits and CMOS gate arrays. The multi-channel prosthesis has undergone a clinical trial on four postlingually deaf patients with profound-total hearing losses. The speech perception results indicate that they were able to obtain open-set speech recognition scores for phonetically balanced words, CID sentences and spondees. In all cases the tests showed significant improvements when using the cochlear prosthesis combined with lipreading compared to lipreading alone.
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ItemA multi-channel cochlear prosthesis for profound-to-total hearing loss( 1984)A multi-channel cochlear prosthesis for profound-total hearing loss has been developed by the University of Melbourne and Nucleus Limited. Clinical trials have shown that the prosthesis provides significant help for postlingually deaf adult patients (lost hearing after normal language patterns have been established). The prosthesis helps the patients understand running speech when combined with lipreading, and a proportion obtain significant open-set speech scores for electrical stimulation alone. The patients with these open-set score can use the device in situations where lipreading is not possible, for example, to converse over the telephone. The prosthesis consists of an externally worn, pocket-sized speech-processor, a headset and an implanted receiver/stimulator and electrode array. The headset contains an .ear-level directional microphone that picks up the speech signal. The speech processor encodes the speech as a series of electrical pulses on the electrode array. The data describing these pulses and the power required to produce them, are sent to the receiver/stimulator from .a radio-frequency coil mounted on the headset. The receiver/stimulator decodes the data and delivers the speech signal as a series of biphasic electrical pulses to the 22 electrodes which have been gently passed along the scala tympani during implantation.
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ItemClinical trial of a multi-channel cochlear prosthesis: results on 10 postlingually deaf patients( 1984)The clinical trial of a multi-channel cochlear prosthesis has been carried out on 10 profoundly-totally deaf adult patients. Speech perception tests have shown that all the patients received significant benefit from the device. They obtained improvements in understanding running speech from 47% to 550% when using the device in conjunction with lipreading compared to lipreading alone. With an open-set CID sentence test, three patients obtained scores showing an ability to understand speech without the need to lipread, and a further three patients had scores indicating they could also receive useful information without lipreading. In two patients, very limited open-set scores for electrical stimulation alone were obtained. This was most probably due to the fact that only a few channels of stimulation were possible due to cochlear disease and they were therefore receiving information more like a single-channel device. The prosthesis has also been found to provide considerable help in hearing and recognizing everyday sounds.
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ItemUnderlying dimensions and individual differences in auditory, visual, and auditory-visual vowel perception by hearing-impaired children( 1984)Abstract not available due to copyright.
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ItemAn acoustic model of a multiple-channel cochlear implant( 1984)Abstract not available due to copyright.
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ItemSpeech processing studies using an acoustic model of a multiple-channel cochlear implant( 1984)Abstract not available due to copyright.
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ItemProsthetic devices for the management of patients with severe sensorineural deafness( 1977)It is estimated that 5-10% of patients with significant hearing loss do not get satisfactory help with a hearing aid. This means that in Australia there are about 5,000-10,000 people who need further treatment. Furthermore, a large number of these patients are born deaf and their proper management is critical if they are going to develop adequate speech and language. If these patients are going 10 perceive speech, the speech must be broken down into signals that can be used 10 stimulate the residual hearing, excite the auditory nerve fibres by electrical stimulation or stimulate another sensory system such as vision or the skin senses. These alternatives offer real hope for the patient with severe sensori-neural deafness as there is a great deal of redundancy in the speech signal. This is illustrated in Fig. 1 which shows the raw signal obtained on a cathode ray oscilloscope for the word "ear". It can be seen that there is an overall waveform envelope which is now thought to be quite important in speech perception. Inside the speech waveform there are waves of many shapes and sizes. Far too many for your eye to detect at a glance, and indeed too many for your ear to perceive. In fact, when you hear phonemes and words your brain only picks up key signals.
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ItemA neurophysiological assessment of the surgical treatment of perceptive deafness( 1970)The results of treating patients with middle ear disease are now good, but the situation is not as satisfactory with perceptive deafness, and this is one of the major problems facing otologists today.
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ItemHearing due to electrical stimulation of the auditory system( 1969)One of the major problems facing otologists today is the treatment of perceptive deafness. The results of treating patients with deafness due to middle-ear disease are now good, but this is not the case when there is damage to the inner ear or central auditory pathways. A hearing aid will assist a great many people, but there are a number of patients with very severe or total deafness who cannot be helped in this way. Consequently, a different approach to the problem must be made, and for this reason, electrical stimulation of the cochlea or auditory pathways to reproduce the natural stimulus may provide a solution.