Graeme Clark Collection
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ItemPreliminary results on spectral shape perception and discrimination of musical sounds by normal hearing subjects and cochlear implantees( 1997)This paper presents an overview of an ongoing research project investigating the perception of musical timbre by people with normal hearing, impaired hearing, and cochlear implants. The investigation of musical timbre has been limited to the perception of steady-state frequency spectra from 10 different sources, including sampled acoustic instruments, sung vowels, and synthetic waveforms. Subjects were tested in three different tasks: I) the discrimination of spectra when presented in all possible pairs; 2) the measurement of the internally-perceived frequency spectra using a forward-masking paradigm; and 3) the identification of the spectra by name with the restricted set of sound sources from which they were sampled. Preliminary results from the normally hearing subjects show the spectra to be 99.8% distinguishable, and that significant detail is evident in the internal spectral envelopes from different sounds. There was around 50%-correct identification of stimuli by name with the original sound sources from which they were sampled. The experimental work with hearing impaired and cochlear implant subjects has commenced.
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ItemRehabilitation strategies for adult cochlear implant users(Monduzzi Editore, 1997)This paper summarizes open-set speech perception results using audition alone for a large group of adult Nucleus cochlear implant users in Melbourne. The results show wide variation in performance but significant improvement over the years from 1982 to 1995. Analysis of these results shows that speech processor developments have made the major contribution to this improvement over this time. Recent results for patients using the SPECTRA-SPEAK processor show !hat most subjects obtain good speech perception within six months of implantation and the need for intensive auditory training is minimal for many of these patients. Postoperative care should encourage consistent device use by providing opportunities for success and providing long term technical support for implant users. In some cases, including elderly patients, those with long term profound deafness, and those with special needs, there will still be a need for additional rehabilitation and auditory training support.
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ItemFactors affecting outcomes in children with cochlear implants(Monduzzi Editore, 1997)Open-set speech perception tests were completed for a group of 52 children and adolescents who were long-term users of the Nucleus multiple channel cochlear prosthesis. Results showed mean scores for the group of 32.4% for open-set BKE sentences and 48.1% for phonemes in open-set monosyllabic words. Over 80% of the group performed significantly on these tas1cs. Age at implantation was identified as a significant factor affecting speech perception performance with improved scores for children implanted early. This factor was evident in the results at least down to the age of three years. Duration.. of profound hearing loss, progressive hearing loss, educational program and preoperative residual hearing were also identified as significant factors that may affect speech perception performance.
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ItemCochlear implant speech processing for severely-to-profoundly deaf people( 1996)A cochlear implant is a device which restores some hearing in severely-to-profoundly deaf people when the organ of Corti has not developed or is destroyed by disease or injury to such an extent no comparable hearing can be obtained with a hearing aid. When the organ of Corti is severely malfunctioning or absent, sound vibrations cannot be transduced into temporo-spatial patterns of action potentials along the auditory nerve for the coding of frequency and intensity. As a result, a hearing aid which amplifies sound, is of little or no use.
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ItemPsychophysical studies in children and the developing auditory system [Abstract]( 1995)A number of psychophysical studies have been conducted on cochlear implant patients who became deaf early in life. The implant prosthesis manufactured by Cochlear Pty. Limited was used. The aims of these studies have been to compare the performance of early-deafened and postlinguistically deafened adult patient groups, and to determine any relationships between the performance of early-deafened patients and variables that may influence performance, such as duration of deafness and age at implantation. The studies have also been concerned with the development of appropriate test procedures for early-deafened patients, who vary considerably in age arid cognitive ability.
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ItemElectrophonic response characteristics to electrical stimulation of the cochlea [Abstract]( 1996)Speech recognition results of profoundly deaf cochlear implant patients are on average better than those for severely-to-profoundly deaf patients using acoustic hearing aids. It is therefore increasing likely that implant patients may have some residual hearing that could be incorporated into speech processing strategies with the potential to further improve speech recognition. Electrical stimulation of the cochlea results in direct and electrophonic excitation of auditory nerve fibres. Auditory nerve compound action potential (CAP) forward masking studies show the level of frequency specific electrophonic stimulation is highly correlated with the spectral energy of the electrical stimulus waveform.
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ItemFricative perception by cochlear implant users( 1992)Three implant users were tested with 45 syllables consisting of[v, f, �, ?, z, s, ?, ?, d?, t ?, ?, , d, n, 1] before the vowels [I ,a,u] with three wearable speech processors. The WSP3 processor coded first and second formant frequencies and amplitudes. The MSP1 processor used a similar scheme with improved measurement and coding of the formants. The MSP2 processor added amplitude information from three higher frequency bands. Average scores were 42% for WSP3, 54% for MSP1, and 57% for MSP2. Perception of voicing, manner, and place of articulation of the consonants was significantly greater for the MSP processors than the WSP3 processor. Place perception was slightly higher for MSP2 than MSP1. The listeners used three perceptual dimensions which were highly correlated with the frequencies and amplitudes of peaks in the low frequency region of the frication spectrum, amplitudes of high frequency peaks, and duration of the frication noise.
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ItemExperimental research into cochlear implants( 1977)The areas of research to be discussed are studies of animal behaviour, cochlear models, multiple electrode arrays and experimental surgery.