Graeme Clark Collection
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ItemA multiple-channel cochlear implant: an evaluation using open-set CID sentences( 1981)A multiple-channel cochlear implant and speech processor have been used in two postlingually deaf adult patients with a total hearing loss, to enable them to perceive varying degrees of running speech. The results have been confirmed with open-set CID everyday sentence tests. Using the implant alone, the patients obtained 8% and 14% scores with pre-recorded material, and 34% and 36% scores for "live" presentations. This was equivalent to the perception of 35% of connected discourse. When the implant was used in conjunction with lipreading, improvements of 188% and 386% were obtained over lipreading alone, and the scores were 68% and 98% which were equivalent to the perception of 60% and 95% of connected discourse.
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ItemDesign criteria of a multiple-electrode cochlear implant hearing prosthesis( 1978)Abstract not available due to copyright.
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ItemSpeech results with a bilateral multi-channel cochlear implant subject for spatially separated signal and noise( 1999)Speech tests in noise were administered to a bilaterally implanted cochlear implant subject. Performance for simultaneous use of two identical implants, with the same speech processing strategy on two independent standard clinical processors, was compared with that of the better performing monaural side alone. Speech was presented at an angle of 45 degrees toward one ear, with noise at 45 degrees toward the contralateral side. Tests were also administered for speech and noise reversed in location. When the speech signal was on the same side as the subject's better performing ear, monaural and binaural tests resulted in similar scores. When the speech was on the opposite side, however, the binaural condition showed significantly better speech scores. The results indicate that binaural implants can provide improved performance in noise when speech and noise arc spatially separated.
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ItemSpeech perception in implanted children: influence of preoperative residual hearing on outcomes [Abstract]( 1998)Since the first child was implanted with the Nucleus 22-channel prosthesis in Melbourne in 1985, several thousand children world-wide have now benefitted from this technology. More effective paediatric assessment and management procedures have now been developed, allowing cochlear implants to be offered to children under the age of 2 years. Improvements in speech processing strategy have also been implemented in the Nucleus implant system, resulting in increased mean speech perception benefits for implanted adults. Although a range of performance on formal measures of hearing, speech or language has been reported for children using implants, results from the first decade of implant experience consistently show that significant benefits are available to children receiving their implant at an early age. Reported speech perception results for implanted children show that a considerable proportion (60%) of paediatric patients in the Melbourne and Sydney clinics are able to understand some open-set speech using electrical stimulation alone. These results, and the upward trend of mean speech perception benefits shown for postlinguistically deafened adults have raised questions as to whether severely, or severely-to-profoundly deaf children currently using hearing aids would in fact benefit more from a cochlear implant. To investigate the potential influence of the degree of preoperative residual hearing on postoperative speech perception, results for all implanted children in the Melbourne and Sydney cochlear implant programs were analysed. Results showed that as a group, children with higher levels of preoperative residual hearing were consistently more likely to achieve open-set speech perception benefits. Potential factors in this finding could be higher levels of ganglion cell survival or greater patterning of the auditory pathways using conventional hearing aids prior to implantation. Conversely, children with the least preoperative residual hearing were less predictable, with some children achieving open-set perception, and others showing more limited closed-set benefits to perception. For these children, it is likely that preoperative residual hearing is of less significance than other factors in outcomes.
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ItemComparison of the SPEAK (Spectral Maxima) and multipeak speech processing strategies and improved speech perception in background noise( 1995)As more is known about speech processing for Cochlear Implant patients, results should continue to improve. It now appears possible that Cochlear Implant patients may, in some instances, reach performance levels that are better than those obtained by most severely deaf people who use hearing aids.
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ItemCombined cochlear implant and speech processing hearing aid for implant users with a severe to profound hearing loss in the contralateral ear [Abstract]( 1994)The bimodal device was developed for cochlear implant users who simultaneously wear a hearing aid in the opposite ear having residual hearing of a severe to profound degree. The aim was to create a single device to provide both input signals in a more compatible manner and thus maximise use of the individual's total hearing capabilities. The acoustic component of the bimodal device is very flexible and can implement various speech processing strategies with speed, ease and precision. The Frequency Response Tailoring strategy utilises three filters to fit a frequency gain curve to within 1-2 dB of that desired. Modifications at discrete frequencies, ranges or slopes can be readily made. The Peak Sharpening or Spectral Enhancement strategy amplifies the formant peaks in speech for potential improvement of formant resolution and speech perception in the presence of background noise. The Resynthesis strategy presents specifically selected components of speech in selected combinations and includes the ability to transpose higher frequency information to lower frequency ranges for individuals with no aidable high frequency hearing levels. Different fits can be quickly and easily interchanged for comparison and evaluation and subsequent modifications indicated can be readily effected. Any combination of acoustic and implant speech processing strategy can be presented to optimise speech perception for the individual user.
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ItemThe development of the Melbourne/Cochlear multiple-channel cochlear implant for profoundly deaf children( 1992)In 1978-79, a speech processing strategy which extracted the voicing (FO) and second formant (F2) frequencies and presented these as rate and place of stimulation respectively to residual auditory nerve fibres was developed for the University of Melbourne's prototype multiple-channel receiver-stimulator (Clark et aI1977, Clark et a11978, Tong et aI1980). This speech processing strategy was shown to provide post linguistically deaf adults with some open-set speech comprehension using electrical stimulation alone, and considerable help when used in combination with lipreading (Clark et al 1981).
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ItemPreliminary results with a six spectral maxima speech processor for The University of Melbourne/Nucleus multiple electrode cochlear implant( 1991)An improved sound processor for a multiple-channel cochlear implant hearing prosthesis has been developed. The spectral maxima sound processor (SMSP) extracts the six largest frequency components of speech and presents stimuli at a rate of 250 Hz to electrodes at positions selected on the basis of the spectral frequencies. It was designed for use initially with the advanced cochlear implant recently developed at the University of Melbourne, which is capable of high rate and quasi-simultaneous stimulation. The present study, however, was carried out with two subjects who have the more widely used 22-electrode implant produced commercially by Cochlear Pty Limited (formerly Nucleus Limited). Preliminary results comparing the performance of the SMSP with that of previous speech processing techniques (F0/F1/F2 strategy) are presented. The results indicate that the SMSP is capable of providing implanters with significantly greater information about speech.
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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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ItemSpeech processing for cochlear implant prostheses( 1984)The transformation of speech into electrical signals which can stimulate the auditory nerve in order to create hearing sensations that carry speech information depends on many factors. These include the limitations imposed by the current state-of-the-art in otological surgery, microelectronic and micromechanical technology, and knowledge of the functioning of the auditory system under both acoustic and electrical stimulation. Sufficient advances have been made in all these areas to enable several research centers to develop cochlear prostheses which give some hearing to certain totally deaf persons. The work of these centers towards the goal of full unaided speech perception via the prosthesis is examined and evaluated.