Graeme Clark Collection
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ItemSpeech cues for cochlear implantees: spectral discrimination(Monduzzi Editore, 1997)The relationship between the ability of cochlear implantees to perceive speech and their ability to discriminate between stimulation on adjacent electrodes was investigated. Speech perception ability was assessed with monosyllabic words in 8 users Nucleus cochlear prosthesis. The ability of these subjects to discriminate between stimulation on adjacent electrodes, in of random loudness differences between electrodes was determined. Results were averaged in the apical, mid and basal regions of the cochlea. Regression analysis showed that speech perception ability and electrode discrimination ability were correlated in the apical to mid region of the cochlea. but the two factors were not correlated in the basal region. Therefore, these results suggest that implantees require the ability to discriminate between stimulation on adjacent electrodes in the apical to mid region of the cochlea in order to achieve high speech perception scores.
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ItemSpeech perception of hearing aid users versus cochlear implantees(Monduzzi Editore, 1997)Recent improvements in speech recognition abilities for profoundly deaf cochlear implantees suggests that some adults with a severe hearing impairment might benefit from a cochlear implant. Unfortunately, no studies have directly compared the speech perception abilities of the severely hearing impaired with those of cochlear implant users. An investigation of the speech perception performance of people with a severe hearing loss, who use hearing aids, was conducted in the Department of Otolaryngology at The University of Melbourne. Each participant (n=35) took part in a series of speech perception tests which included 11 vowel recognition tests, CNC words, CUNY sentences, and the Connected Speech Test. The results from these severely hearing impaired persons were compared to results from cochlear implant users. The group of severely hearing impaired adults performed better on tests of vowel and word perception but poorer on tests of open set sentence perception in comparison to a group of cochlear implant users.
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ItemSpeech perception in implanted children: effects of speech processing strategy and residual hearing(Mendoza Editor, 1997)The ability of implanted children to adapt to different speech processing strategies has been demonstrated for the Nucleus implant system. Children previously experienced with the Multipeak speech processing strategy. were able to gain significant improvements in consonant, word and sentence perception using the Speak speech processing strategy. suggesting some degree of neural plasticity in neural-auditory coding. Of 192 implanted children with different degrees of preoperative residual hearing, 65% were found to obtain significant scores on open-set speech materials using electrical stimulation alone. Those children with more residual hearing had a greater probability of achieving open-set understanding and at a minimum level, perceived high frequency consonant information which would not have been available through conventional hearing aids.
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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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ItemAn extension of the Multipeak speech processing strategy for the MSP/MINI 22 cochlear implant system( 1992)The speech perception of three post-linguistically deaf adults using the Nucleus MSP/Mini System 22 cochlear implant system programmed with a new speech processing strategy, MPEAK+AO. was evaluated. The MPEAK+AO strategy retains all the information of the standard Multipeak speech processing strategy and additionally presents acoustic components below 400Hz to the most-apical electrode. This extra spectral Information may help implantees understand speech, particularly in noise. Since the estimated fundamental frequency is presented as the rate of stimulation at a fixed intracochlear site and is thereby potentially perceived more easily. and the amplitude of the stimulation on the apical electrode, associated with the voice fundamental, Is directly determined from the estimated energy in the relevant spectral region. these coding factors may provide a better representation ot the prosodic information in speech and a more complete auditory feedback signal. The comparison between Multipeak and MPEAK+AO included tests of vowel, consonant and CNC word recognition. Speech materials were presented with both a male and female speaker. Sentence material. presented with background masking noise (four-speaker babble) was also used. The results showed that the new strategy significantly improved the ability of these MSP users to recognise words in open-set sentences in noisy conditions.