Graeme Clark Collection
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ItemPreliminary evaluation of a formant enhancement algorithm on the perception of speech in noise for normally hearing listeners( 1994)The effects on speech perception in noise of dynamic filtering with bandpass filters centred at the first formant (f1) and second formant (f2) frequencies were evaluated with four normally hearing listeners. Multitalker babble was added to the speech signal with signal-to-noise ratios of-5 to -15 dB, chosen to reduce intelligibility to about 50%. The combined signal was then filtered with two-pole programmable bandpass filters centred at fl and f2 under the control of a real-time speech processor. The f1 and f2 frequencies were estimated from the speech signal before noise was added to avoid hardware processing errors. Closed set vowel and consonant tests (using 11/h/vowel/d/ and 12 /a/consonant/a/ stimuli), the Consonant-Nucleus-Consonant Monosyllabic Word Test and the Bamford-Kowal-Bench Sentence Test were carried out for three filter bandwidths (3/4, 1/3 and 1/6 octave) and for unprocessed speech in noise. The processing produced a small significant improvement for vowels in all three processed speech conditions and for monosyllables at the broadest filter setting compared to the unprocessed speech condition. There was no significant effect on consonants. A small negative effect was observed for sentences at the narrowest filter setting.
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ItemCochlear implants for congenitally deaf adolescents: is open-set speech perception a realistic expectation?( 1994)The prognosis for benefit from use of cochlear implants in congenitally deaf adolescents, who have a long duration of profound deafness prior to implantation, has typically been low. Speech perception results for two congenitally deaf patients implanted as adolescents at the University of Melbourne/Royal Victorian Eye and Ear Hospital Clinic show that, after 12 months of experience, both patients had significant open-set speech discrimination scores without lipreading. These results suggest that although benefits may in general be low for congenitally deaf adolescents, individuals may attain significant benefits to speech perception after a short period of experience. Prospective patients from this group should therefore be considered on an individual basis with regard to prognosis for benefit from cochlear implantation.
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ItemCochlear implants in children, adolescents, and prelinguistically deafened adults: speech perception( 1992)A group of 10 children, adolescents, and prelinguistically deafened adults were implanted with the 22-electrode cochlear implant (Cochlear Pty Ltd) at the University of Melbourne Cochlear Implant Clinic and have used the prosthesis for periods from 12 to 65 months. Postoperative performance on the majority of closed-set speech perception tests was significantly greater than chance, and significantly better than preoperative performance for all of the patients. Five of the children 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 5 children were implanted during preadolescence (aged 5:5 to 10:2 years) and the fifth, who had a progressive loss, was implanted during adolescence (aged 14:8 years). The duration of profound deafness before implantation varied from 2 to 8 years. Improvements were also noted over postoperative data collection times for the younger children. The remaining 5 patients who did not demonstrate open-set recognition were implanted after a longer duration of profound deafness (aged 13:11 to 20:1 years). The results are discussed with reference to variables that may affect implant performance, such as age at onset of loss, duration of profound loss, age at implantation, and duration of implantation. They are compared with results for similar groups of children using hearing aids and cochlear implants.
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ItemSpeech perception, production and language results in a group of children using the 22-electrode cochlear implant( 1992)Five children out of a group of nine (aged 5.5 to 19.9 years) implanted with the 22-electrode cochlear implant (Cochlear Ply. Ltd.) have achieved substantial scores on open-set speech tests using hearing without lipreading. Phoneme scores for monosyllabic words ranged from 40% to 72%. Word scores in sentences ranged from 26% to 74%. Four of these five children were implanted during preadolescence. The fifth child, who had a progressive loss and was implanted during adolescence after a short period of very profound deafness, scored highest on all speech perception tests. The remaining four children who did not demonstrate open-set recognition were implanted during adolescence after a long duration of profound deafness. Post-operative performance on closed-set speech perception tests was better than pre-operative performance for all children. Improvements in speech and language assessments were also noted. These improvements tended to be greater for the younger children. The results are discussed with reference to variables which may contribute to successful implant use: such as age at onset, duration of profound hearing loss, age at implantation, aetiology, educational program, and the type of training provided.
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ItemThe effect of handedness in tactile speech perception( 1993)This study examined differential performance of normally hearing subjects using a tactile device on the dominant versus non-dominant hand. The study evaluated whether tactual sensitivity for non-speech stimuli was greater for the dominant hand as compared with the non-dominant hand, and secondly, whether there was an advantage for speech presented tactually to the dominant hand, resulting from a preferential pathway to the language processing area in the left cerebral hemisphere. Evaluations of threshold pulse width, dynamic ranges, paired electrode identification, and a closed-set tactual pattern discrimination test battery showed no difference in tactual sensitivity measures between the two hands. Speech perception was assessed with closed sets of vowels and consonants and with open-set Harvey Gardner (HG) words and Arthur Boothroyd (AB) words. Group mean scores were higher in each of the tactually aided conditions as compared with the unaided conditions for speech tests, with the exception of AB words in the tactile plus lip-reading plus audition/lip-reading plus audition condition on the right hand. Overall mean scores on the closed-set vowel test and on open-set HG and AB words were significantly higher for the tactually aided condition as compared with the unaided condition. Comparison of performance between the dominant and non-dominant hand showed a significant advantage for the dominant hand on the closed-set vowel test only. No significant differences between hands in either tactually aided or unaided conditions were evident for any of the other speech perception tests. Factors influencing this result could have been variations in degree of difficulty of the tests, the amount of training subjects received, or the training strategy employed. Although an advantage to presenting speech through the dominant hand may exist, it is unlikely to be great enough to outweigh possible restrictions on everyday use.
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ItemCochlear implants in children, adolescents, and prelinguistically deafened adults: speech perception( 1992)A group of 10 children, adolescents, and prelinguistically deafened adults were implanted with the 22-electrode cochlear implant (Cochlear Ply Ltd) at the University of Melbourne Cochlear Implant Clinic and have used the prosthesis for periods from 12 to 65 months. Postoperative performance on the majority of closed-set speech perception tests was significantly greater than chance, and significantly better than preoperative performance for all of the patients. Five of the children 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 5 children were implanted during preadolescence (aged 5:5 to 10:2 years) and the fifth, who had a progressive loss, was implanted during adolescence (aged 14:8 years). The duration of profound deafness before implantation varied from 2 to 8 years. Improvements were also noted over postoperative data collection times for the younger children. The remaining 5 patients who did not demonstrate open-set recognition were implanted after a longer duration of profound deafness (aged 13:11to 20:1 years). The results are discussed with reference to variables that may affect implant performance, such as age at onset of loss, duration of profound loss, age at implantation, and duration of implantation. They are compared with results for similar groups of children using hearing aids and cochlear implants.
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ItemTactile-auditory speech perception by unimodally and bimodally trained normal-hearing subjects( 1993)The following study compared the effectiveness of unimodal and bimodal training strategies at improving the perception of speech information under a variety of conditions. Normal hearing subjects were trained in the perception of vowel and consonant stimuli. Speech information was provided either via a multiple channel electrotactile speech processing aid (the Tickle Talker), and/or by a 200-Hz low-pass filtered auditory signal. Two subjects were trained only in the combined tactile-plus-auditory (TA) condition; the remaining two were trained in both the tactile-alone (T) and auditory-alone (A) conditions; however, only one condition was used at any single time. All subjects were evaluated in the TA, T, and A conditions, both at the beginning of the study, prior to training, and at the completion of training, on closed-set vowel and consonant confusion tests, and on an open-set word test. Results indicated that whilst statistically significant improvements occurred from one evaluation period to the next, in both groups of subjects, the improvements per condition were not dependent on the type of training received. The results provide a preliminary indication that the provision of unimodal training does not impair the perception of speech information under bimodal perception conditions.
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ItemPerception of multiple electrode stimulus patterns: implications for design of an electrotactile speech processor( 1991)Abstract not available due to copyright.
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ItemPerception of sentences, words, and speech features by profoundly hearing-impaired children using a multichannel electrotactile speech processor( 1990)Abstract not available due to copyright.
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ItemSpeech feature recognition by profoundly hearing impaired children using a multiple-channel electrotactile speech processor and aided residual hearing( 1990)Abstract not available due to copyright.