Graeme Clark Collection
Permanent URI for this collection
Search Results
1 - 9 of 9
-
ItemContributing factors to improved speech perception in children using the nucleus 22-channel cochlear prosthesis( 1997)It has been established that use of multiple-channel intracochlear implants can significantly improve speech perception for postlinguistically deafened adults. In the development of the Nucleus 22-channel cochlear implant, there have been significant developments in speech processing strategies, providing additional benefits to speech perception for users. This has recently culminated in the release of the Speak speech processing strategy, developed from research at the University of Melbourne. The Speak strategy employs 20 programmable bandpass filters which are scanned at an adaptive rate, with the largest outputs of these filters presented to up to ten stimulation channels along the electrode array. Comparative studies of the Speak processing strategy (in the Nucleus Spectra-22 speech processor), with the previously-used Multipeak (Multipeak) speech processing strategy (in the Minisystem-22 speech processor), with profoundly deaf adult cochlear implant users have shown that the Speak processing strategy provides a significant benefit to adult users both in quiet situations and particularly in the presence of background noise. Since the first implantation of the Nucleus device in a profoundly hearing-impaired child in Melbourne in 1985, there has been a rapid growth in the number of children using this device. Studies of cochlear implant benefits for children using the Nucleus 22-channel cochlear implant have also shown that children can obtain significant benefits to speech perception, speech production and language, including open-set understanding of words and sentences using the cochlear implant alone. In evaluating contributing factors to speech perception benefits available for children, four specific factors are important to investigate: (1) earlier implantation -resulting from earlier detection of deafness; (2) improved hardware and surgical techniques -allowing implantation in infants; (3) improved speech processing, and (4) improved habilitation techniques. Results reported previously have been recorded primarily for children using the Multipeak strategy implemented in the MSP speech processor. While it is important to evaluate the factors which might contribute to improvements in speech perception benefits, an important question is the effect of improved speech processing strategy, since this will determine what is perceived through the device. Given that adult patients changing to the Spectra speech processor had also shown improved perception in noisy situations, and the fact that children are in general in noisy environments in the classroom setting for a large proportion of their day, it was of obvious interest to evaluate the potential for benefit in poor signal-to-noise ratios from use of the Speak processing strategy and from specific training in the ability to perceive in background noise. The study was aimed at evaluating whether children who were experienced in use of the Multipeak speech processing strategy would be able to changeover to the new Speak processing strategy, which provides a subjectively different output. Secondly, the study aimed to evaluate the benefits which might accrue to children from use of controlled habilitation in background noise.
-
ItemDesign fundamentals for electrotactile devices: the Tickle Talker case study(Whurr, 1995)Since the work of Gault in the 1920s, the literature has chronicled the development of numerous tactile devices for use by the hearing impaired in improving communication. Devices have been developed to target improvements in both speech perception and speech production. In each development, the inventors have attempted to encode speech information through stimulation of the intact kinaesthetic system of the individual, as a supplement or replacement for speech input available from the damaged auditory pathway.
-
ItemResearch in auditory training(Academy of Rehabilitative Audiology, 1994)Speech perception and communication can improve as a result of experience, and auditory training is one way of providing experiences that may be beneficial. One of the most important factors influencing the effectiveness of auditory training is the amount of experience the client already has. Other factors include the severity of the hearing loss, the sensory device used, the environment, personal qualities of the client and clinician, the type of training, and the type of evaluation used. Despite a long history of clinical practice, the effects of these factors have been investigated in few controlled studies. Even in special cases where training has an obvious role, such as adults using cochlear implants, there has been little objective comparison of alternative training methods. One reason for this is the difficulty of carrying out definitive experiments that measure changes in performance over time in the presence of many confounding variables. These variables may also help to explain the apparently contradictory results that can be found in the literature on auditory training and in the diverse points of view expressed by practicing clinicians. Issues and methods appropriate for research in auditory training among adult clients are discussed with reference to the needs of modem clinical practice.
-
ItemThe spectral maxima sound processor: recent findings in speech perception and psychophysics(Wien, 1994)The Spectral Maxima Sound Processor (SMSP) was developed at the University of Melbourne for use with the Mini System 22 implant manufactured by Cochlear Pty Ltd. The SMSP has been shown in recent studies to provide improved speech perception to implantees when compared to the currently commercially available processor for this implant (the MSP (MULTIPEAK) processor). In the first of three experiments, the effect on speech perception of increasing the rate of stimulation of the SMSP and of increasing the number of electrodes activated in each stimulation cycle was studied. It was found that these parameter changes made little difference to speech perception in quiet but both changes were advantageous for some subjects when listening in noise. The second and third experiments investigated psychophysically the effects of two aspects of the SMSP strategy which differ from previous processors for this implant. In the second experiment, it was found that concurrent stimulation of two adjacent or nearby electrodes evoked a pitch which was intermediate to that of either electrode. This may explain, in part, the better discrimination of vowel formants by users of the SMSP. In the third experiment, it was found that a pitch related to the modulation frequency was evoked by amplitude-modulating a constant rate stimulus, provided that the rate of stimulation was sufficiently high (four times the modulation frequency) or a multiple of the modulation frequency. This result may explain the equal ability of SMSP and MSP users to perceive speaker differences and intonation patterns, even though the rate of stimulation is constant In the SMSP.
-
ItemSpeech perception for adults using cochlear implants(Whurr, 1994)A mere 16 years ago, the title of this chapter would have created considerable consternation in audiological circles. A high proportion of otologists and audiologists would have wondered, with good reason, about the potential content of such a chapter. In 1977, there were certainly cochlear implants in use with reported benefits, but reliable documentation of any useful speech perception under controlled conditions was difficult to find. The rapid development of cochlear prostheses since that time has led to thousands of profoundly hearing-impaired adults obtaining benefits for speech perception, and there is now no doubt regarding the efficacy of such devices. This chapter will provide a brief overview of this rapid improvement in the speech perception of adult cochlear implant users, consider some of the reasons for this improvement, and discuss some of the factors that may influence speech perception performance for the individual user. (From Introduction)
-
ItemHabilitation issues in the management of children using the cochlear multiple-channel cochlear prosthesis(Wien, 1994)Since 1985, a significant proportion of patients seen in the Melbourne cochlear implant clinic have been children. The children represent a diverse population, with both congenital and acquired hearing-impairments, a wide-range of hearing levels pre-implant, and an age range from 2 years to 18 years. The habilitation programme developed for the overall group must be flexible enough to be tailored to the individual needs of each child, and to adapt to the changing needs of children as they progress. Long-term data shows that children are continuing to show improvements after 5-7 years of device use, particularly in their perception of open-set words and sentences. Habilitation programs must therefore be geared to the long-term needs of children and their families. Both speech perception and speech production need to be addressed in the specific content of the habilitation program for any individual child. In addition, for young children, the benefits of improved speech perception should have an impact on development of speech and language, and the focus of the programme for this age child will reflect this difference in emphasis. Specific materials and approaches will vary for very young children, school-age and teenage children. In addition, educational setting will have a bearing on the integration of listening and device use into the classroom environment.
-
ItemSpeech processing for cochlear implants(JAI Press Ltd, 1992)The cochlear implant is a hearing prosthesis designed to replace the function of the ear. The operation of the prosthesis can be described as a sequence of four functions: the processing of the acoustic signal received by a microphone; the transfer of the processed signal through the skin; the creation of neural activity in the auditory nerve; and the integration of the experience of this neural activity into the perceptual and cognitive processing of the implantee.
-
ItemComparison of current speech coding strategies( 1993)This paper reports on two studies carried out at the University of Melbourne jointly with Cochlear Pty Ltd. The studies demonstrated substantial speech perception improvements over the current Multipeak strategy in background noise.
-
ItemPreliminary speech perception results for children with the 22-electrode Melbourne/ cochlear hearing prosthesis( 1993)The 22-electroce cochlear prosthesis developed by the University of Melbourne and Cochlear Pty. Ltd. has been shown to provide significant speech perception benefits to profoundly deafened adults. More recently, use of an improved Multipeak encoding strategy has significantly improved speech perception performance both in quiet and in noise. Benefits to speech perception in children have not as yet been fully documented, in part due to the shorter history of implant use in children and the smaller overall number of children implanted as compared with adults. The first implantation of the 22-electrode cochlear prosthesis in a child was carried out in Melbourne in January of 1985. In Melbourne, a 5-year-old child was operated on in April 1986, and a first congenitally deaf child in April 1987. The age of implantation has been progressively reduced, with the first 2-year-old child implanted in Melbourne in 1990. As at January 1992, approximately 1,200 children (under 18 years of age inclusive) have been implanted worldwide with the 22-electrode cochlear prosthesis. Of this number, approximately 50% are under the age of 6 years. The age of the child, aetiology of the hearing loss, age at onset and duration of the hearing loss, education program attended both prior to and subsequent to implantation, and parental motivation to assist in habilitation are all factors which may affect an individual child's development and progress with the device. Evaluation of performance in children is complicated by a number of issues, including the effects of delayed speech and language development, and the ability of individual children to perform auditory tests. The measure of performance chosen for any evaluation will also reflect the interests of the particular clinician. For example, effects of device use on speech production may be of interest to the speech therapist, whereas educational progress will be of primary importance to the teacher of an implanted child. However, in choosing an appropriate evaluation test to measure progress woth the cochlear prosthesis, it is vital to realize that all measures such as effects of device use on speech production, educational progress, development of language, and effects on social and communication skills depend on the child being able to accurately perceive speech information through her/his device.