Graeme Clark Collection
Permanent URI for this collection
Search Results
1 - 10 of 19
-
ItemThe effects of electrode position and stimulus period on the hearing sensations in a multiple-channel cochlear implant patient [Abstract]( 1981)Abstract not available due to copyright.
-
ItemPerceptual dissimilarity and discrimination studies using two-electrode stimulation with a multiple-channel cochlear implant patient [Abstract]( 1981)Abstract not available due to copyright.
-
ItemPitch and loudness studies on a multiple-channel cochlear implant patient [Abstract]( 1981)Abstract not available due to copyright.
-
ItemSignal processing for multichannel cochlear implants: past, present and future [Abstract]( 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.
-
ItemA clinical report on vocabulary skills in cochlear implant users [Abstract]( 1994)Receptive vocabulary results are reported for 32 children, adolescents and prelinguistically deafened adults implanted with the 22-electrode cochlear implant at the Melbourne Cochlear Implant Clinic. Age at implantation ranged from 2 years, 6 months to 20 years and implant use ranged from 1 year to 7 years, 8 months. There were significant gains from pre- to postoperative assessments on the Peabody Picture Vocabulary Test (PPVT) for the majority of subjects. Rates of improvement found are compatible with previous reports on smaller numbers of implant users, but cannot be attributable unambiguously to use of the implant. The group postoperative performance was significantly higher than mean preoperative performance (n =25). The relationship of variables such as duration of implant use, duration of profound deafness and speech perception ability to improvement on the PPVT is discussed. Expressive vocabulary results on the Renfrew Word Finding Vocabulary Scale are reported for 11 of the subjects. Less substantial gains were made on this measure.
-
ItemIssues in long-term management of children with cochlear implants and tactile devices [Abstract]( 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.
-
ItemA clinical report on speech production of cochlear implant users [Abstract]( 1994)Speech production results are reported for a group of 15 children, adolescents and prelinguistically deafened adults implanted with the 22-electrode cochlear implant. Age at implantation ranged from 5 years to 20 years and implant experience ranged from 1 year to 4 years, 7 months. On a speech intelligibility test using sentences seven implant users improved significantly over time. Mean group performance (n = 11) improved from 18% preoperatively to 43% postoperatively. Similarly on a test of articulation, eight implant users improved significantly over time and the group mean postoperative performance (n = 11) exceeded the preoperative performance (55% compared to 38%). This group effect was significant for consonants and blends but was nonsignificant for vowels. Improvements occurred for front, middle and back consonants, for stops, nasals, fricatives and glides and for voiceless and voiced consonants. Three implant users showed no significant gain on either test. The results suggest complex relationships between speech production performance and sensory information provided by a multichannel implant.
-
ItemDesign fundamentals for a tactile speech processor: i) encoding of speech information, and ii) biomedical safety considerations [Abstract]( 1992)Approaches to providing speech information through the tactual modality have varied in: number and spatial location of transducers; method of interfacing with the skin's sensory apparatus; and content of speech information presented. Use of a multiple speech feature encoding approach to design of a tactile device was implemented in the wearable multichannel electrotactile speech processor or Tickle Talker developed at the University of Melbourne. Psychophysical studies established that subjects could discriminate salient electrical parameters in the tactual display, and that this information could be used to discriminate acoustic speech feature contrasts. Results with normally-hearing and hearing-impaired adults and children using an FOF2 encoding strategy showed improved discrimination scores for closed-set speech feature discrimination batteries, closed-set vowel and consonant identification tasks, as well as for open-set word and sentence comprehension. Based on analyses of tactual encoding of speech features, alternative speech processing strategies designed to increase the quality of speech information available were evaluated. Results for two hearing-impaired adults showed improved feature discrimination with the addition of a voicing signal to the FOF2 strategy. Biomedical safety investigations conducted concurrently have established that the electrical parameters of the stimulus waveform, electrode handset design, and electrical circuitry of the device are free from potential risks. Longer-term physiological assessments included measures of possible effects of electrical stimulation on tactual sensitivity, finger temperature, finger and hand blood flow, electrical thresholds and maximum comfortable levels, and on central nervous system, function as measured by EEG. Results of the kinesthetic, vascular and neurological assessments showed no significant contraindications which might limit application or long-term use of the device.
-
ItemSpeech feature encoding through an electrotactile speech processor [Abstract]( 1989)Abstract not available due to copyright.
-
ItemSpeech perception results in children using the 22-electrode cochlear implant [Abstract]( 1990)Twenty-one profoundly hearing impaired children ranging in age from 3 to 20 years have been implanted with the 22-electrode cochlear implant (Cochlear Pty ltd) at the University of Melbourne Cochlear Implant Clinic. Five children (aged 6.0 to 14.8 years) have achieved substantial scores on open set speech tests using hearing without lipreading. Phoneme scores in monosyllabic words ranged from 30% to 72%. Word scores in sentences ranged from 26% to 74%. Four of these five children were implanted during preadolescence and the fifth who had a progressive loss, was implanted during adolescence. Eight children (aged 3.0 to 11 years), have either been implanted recently or are too young for detailed assessments. However some have shown using closed set speech perception tests or vowel imitation tasks, that they are beginning to use the auditory input provided by the implant. The remaining children (aged 13.11 to 20.1 years) have not demonstrated open set recognition but are all full time users of the device. This group was implanted during adolescence after a long duration of profound deafness. The results will be discussed with reference to a number of variables which may contribute to successful implant use; such as age of onset of deafness, duration of deafness. age of implantation, educational program and type of training.