Graeme Clark Collection

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    Current trends in speech perception performance in adult cochlear implant patients [Abstract]
    Hollow, Rod ; Plant, Kerrie ; Whitford, Lesley ; Skok, Marisa ; DOWELL, RICHARD ; Clark, Graeme M. ( 1996)
    In 1994, Cochlear Pty. Ltd. (Now Cochlear Limited) released a new speech processor, the Spectra 22, for use with the Nucleus 22-channel cochlear implant. The Spectra 22 speech processor incorporates a new speech processing strategy called SPEAK, which is based upon research conducted by the University of Melbourne. This paper reports post-operative scores on open-set word and sentence materials for adult patients in the Melbourne Cochlear Implant Clinic who have been started up with the Spectra 22 speech processor.
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    Speech perception in people with a severe hearing loss: preliminary results [Abstract]
    Flynn, Mark C. ; Dowell, Richard C. ; Clark, Graeme M. ( 1996)
    Recent improvements in multichannel cochlear implants have led to improved speech perception for people with profound hearing impairments. Given this improvement, it has been suggested that some people with severe hearing impairments would be more successful with a cochlear implant than a hearing aid. Unfortunately little research exists to support the suitability of cochlear implants for these individuals. In order to determine this, a detailed investigation of the aided performance of people with severe hearing losses is being conducted at The University of Melbourne (School of Audiology). Severe hearing loss was defined as a pure tone average of greater than 60dBHL, but no worse that 100dBSPL in the better ear. At present, 15 participants have taken part in this study and their results will be discussed. Each participant took part in a standard audiometric assessment which included an audiogram, AB words, tympanometry with acoustic reflexes and an ABR. Each participant’s hearing aids were assessed to make sure that they were optimally aided. Following the hearing aid evaluation the participants took part in a series of traditional speech perception tests which included 24 consonant recognition, 11 vowel recognition, CNC words, CUNY sentences, and the Connected Speech Test (CSTv2). Other tests of speech perception were conducted which looked at the effects of different types of background noise, amounts of reverberation, rates of speech and amount of available context. The aim of this was to better simulate “real-life” listening conditions. Consequently, a range of results for both traditional assessments of speech perception and simulated listening conditions will be presented and compared.
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    Speech perception for hearing aid users versus cochlear implantees [Abstract]
    Flynn, Mark C. ; Dowell, Richard C. ; Clark, Graeme M. ( 1996)
    Abstract not available due to copyright.
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    Signal processing for multichannel cochlear implants: past, present and future [Abstract]
    DOWELL, RICHARD ; SELIGMAN, PETER ; MCDERMOTT, HUGH ; Whitford, Lesley ; BLAMEY, PETER ; Clark, Graeme M. ( 1994)
    Since the late 1970's, many groups have worked on developing effective signal processing for multichannel cochlear implants. The main aim of such schemes has been to provide the best possible speech perception for those using the device. Secondary aims of providing awareness and discrimination of environmental sounds and appreciation of music have also been considered. Early designs included some that attempted to simulate the normal cochlea. The application of such complex processing schemes was limited by the technology of the times. In some cases, researchers reverted to the use of single channel systems which could be controlled reliably with the existing technology. In other cases, as with the Australian implant, a simple multichannel processing scheme was devised that allowed a reliable implementation with available electronics. Over the next 15 years, largely due to the improvements in integrated circuit technology, the signal processors have slowly become more complex. Further psychophysical research has shown how additional information can be transferred effectively to implant users via electrical stimulation of the cochlea. This has lead to rapid improvement in the speech perception abilities of adults using cochlear implants. Some of the main developments in signal processing over the last 15 years will be discussed along with the latest speech perception results obtained with the new SPEAK processing scheme for the Australian 22-channel cochlear implant. Initial results for SPEAK show mean scores of 70% (equivalent to 85-90% phoneme scores) for open set monosyllabic word testing for experienced adult users. Although there remains a large range of performance for all users of cochlear implants, average speech perception scores for all implanted adults have also improved significantly with the developments in signal processing. It appears likely that multichannel cochlear implants will be a viable alternative for the treatment of severe hearing loss in the future.
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    Issues in long-term management of children with cochlear implants and tactile devices [Abstract]
    COWAN, ROBERT ; DOWELL, RICHARD ; Barker, Elizabeth ; GALVIN, KARYN ; DETTMAN, SHANI ; SARANT, JULIA ; RANCE, GARY ; Hollow, Rod ; BLAMEY, PETER ; Clark, Graeme M. ( 1994)
    For many children with severe and profound hearing losses, conventional hearing aids are unable to provide sufficient amplification to ensure good oral communication and/or in the case of very young children, development of speech and language. Traditionally a number of these children have opted for the use of sign language alone or in Total Communication approaches as a primary means of communication. The advent of multiple channel cochlear implants for children and the continuing development of multiple channel speech processing tactile devices provide auditory approaches to resolving communication difficulties for these children. The successful use of such devices depends on a number of factors including the information provided through the aid; the ease of use, convenience and reliability of the aid; the individual communication needs of the child; and the habilitation and management program used with the device. Long-term data has shown that children continue to show increased speech perception benefits from improvements in speech processing and from further experience with these devices. Habilitation and management programs must therefore be geared to meet the changing needs of children as they progress and of families as children mature and face new challenges. Habilitation must address specific individual needs in speech perception and in speech production. For very young children, benefits of improved speech perception should have an impact on the development of speech and language, and habilitation and management must emphasise the need for language growth.
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    Cochlear implants in children: unlimited potential? [Abstract]
    DOWELL, RICHARD ; Clark, Graeme M. ( 1994)
    Multichannel cochlear implants have been in use for adolescents for 8 years and for children for 6 years. Due to the substantial benefits obtained by postlinguistically deafened adults using multichannel implants, there was a degree of optimism about the potential benefits for profoundly hearing impaired children using these devices. It was speculated that children may adapt more quickly and learn to use information from implants more effectively than adults. On the other hand, there were cautionary predictions that there may be a "critical age", particularly for congenitally or early deafened children, that, once passed, would preclude effective use of auditory information from implants. This age was variously predicted to be anywhere from 2 to 12 years, based on neurophysiological, developmental or psychological arguments. With some years of experience with implanted children, it can now be said that neither the optimistic nor the more cautionary "critical age" predictions have been supported. As with many areas of clinical science, the situation appears to be far more complex than first thought. This paper will discuss the results obtained for 100 children using the multichannel cochlear implant in Sydney and Melbourne in terms of predictive factors, and the potential for the future application of multichannel cochlear implants in children. The results suggest that experience with implant, the number of years of auditory deprivation, the amount of preoperative residual hearing, and the postoperative educational environment may have a significant effect on speech perceptual abilities in implanted children. In addition, approximately 60% of all implanted children show significant open-set speech perception ability with auditory input alone. It is now possible for multichannel cochlear implants to provide auditory skills sufficient for young children to develop functionally normal speech and language through audition, provided consistent, long term habilitation is available.
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    Speech perception with cochlear implants and tactile aids [Abstract]
    Blamey, P. J. ; Clark, Graeme M. ; Dowell, R. C. ( 1988)
    Abstract not available due to copyright.
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    Validation of a technique for establishing maximum comfortable levels for children using cochlear implants [Abstract]
    Hollow, R. ; Winton, L ; Hill, K. ; Dowell, R. ; Clark, Graeme M. ( 2002)
    The aim of fitting a cochlear implant is to establish electrical stimulation parameters that will provide the wearer with comfortable and useful auditory sensations. One parameter that is fundamental to achieving this aim is the Maximum Comfortable Level (C-level). A C-level is the amount of electrical current that produces a loud, but comfortable sound. C-levels need to be established for all channels that a person will use in their speech processor Map. Determining C-levels can be complicated as the person is required to make a judgment about the loudness of a sound. While most adults and older children have the ability to make such a judgment and provide feedback to the clinician, this is rarely the case for young children. Generally, the only way a clinician will be aware a sound could be too loud for a young child is when they observe the child giving an aversive reaction or an involuntary blink. A current level that produces such a reaction is called the Loudness Discomfort Level (LOL). This study examines the relationship between LDLs and C-levels. Testing was performed with a group of adults, using stimulation rates and stimulation modes that are commonly used by children. The LDL/C-level relationship established in this study provides a procedure for selling C-Levels for young children when only loudness discomfort responses can be obtained.
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    Speech perception differences between adults with a substantial hearing impairment and users of multiple-channel cochlear implant [Abstract]
    Flynn, Mark C. ; Dowell, Richard C. ; Clark, Graeme M. ( 1998)
    Decent improvements in the performance of users of multiple-channel cochlear implants has led to speculation that people with a severe or severe-to-profound hearing impairment, may achieve better speech perception with a cochlear implant than with conventional hearing aids. In order to investigate this possibility a detailed investigation of the aided performance of adults with a severe or severe-to-profound hearing impairment was conducted in the Department of Otolaryngology (University of Melbourne). In total thirty-four adults took part in the speech perception tests. To aid statistical analysis and to facilitate discussion, the participants were divided into a severe group (61-80 dB HL) (n = 20) and a severe-to-profound group (81-100 dB HL,) (n = 14). All participants took part in a range of speech perception measures including closed-set vowel and consonant tests, open-set word (CNC) tests, and open-set sentence (CUNY) tests (in quiet conditions and in presence of +10 dB SNR background noise). Comparisons of mean scores were made between the adults with a severe or severe-to profound hearing impairment and a comparable group of multiple channel cochlear implant users. The results indicated that there were significant differences between the groups and that many of these differences were dependent on the types of tests used. Additional discussion will take place regarding the issues involved in providing multiple-channel cochlear implants to adults with a severe or severe-to-profound hearing impairment.