Graeme Clark Collection

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    Speech feature encoding through an electrotactile speech processor [Abstract]
    Cowan, Robert S. C. ; Blamey, Peter J. ; Alcantara, Joseph I. ; Whitford, Lesley A. ; Clark, Graeme M. ( 1989)
    Abstract not available due to copyright.
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    Speech feature recognition with an electrotactile speech processor
    Cowan, R. S. C. ; Blamey, P. J. ; Alcantara, J. I. ; Clark, Graeme M. ; Whitford, L. A. ( 1989)
    The performance of eight subjects was assessed on a closed-set tactual test battery to evaluate efficiency of the speech feature encoding strategy currently used in the University of Melbourne multichannel electrotactile speech processor. The test battery included twelve subtests of suprasegmental and segmental speech feature contrasts. Results showed that all subjects scored significantly above chance on suprasegmental features such as syllable number, stress and vowel length. In addition, seven of the eight subjects scored significantly above chance for vowel formant frequency discrimination. Scores for manner of articulation contrasts were more variable, with better performance for the higher frequency, longer duration fricatives and affricates. Scores for voicing contrasts suggested that improvements to the tactual coding of this feature could be achieved. The second study examined the contribution of the tactual input to consonant feature identification for subjects using the electrotactile aid in combination with either a low-pass filtered auditory input or different levels of aided residual hearing and lipreading. Results for four normally-hearing subjects showed increased voicing and manner identification scores with the addition of tactual input. Similar results were found for two hearing-impaired subjects, one using the tactual input in combination with lipreading and one using the tactual input in combination with aided residual hearing.
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    Speech perception studies using a multichannel electrotactile speech processor, residual hearing, and lipreading
    Cowan, Robert S. C. ; Alcantara, Joseph I. ; Whitford, Lesley A. ; Blamey, Peter J. ; Clark, Graeme M. ( 1989)
    Abstract not available due to copyright.
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    Speech perception using combinations of auditory, visual, and tactile information
    Blamey, Peter J. ; Cowan, Robert S. C. ; Alcantara, Joseph I. ; Whitford, Lesley A. ; Clark, Graeme M. ( 1989)
    Four normally-hearing subjects were trained and tested with all combinations of a highly-degraded auditory input, a visual input via lipreading, and a tactile input using a multichannel electrotactile speech processor. The speech perception of the subjects was assessed with closed sets of vowels, consonants, and multisyllabic words; with open sets of words and sentences, and with speech tracking. When the visual input was added to any combination of other inputs, a significant improvement occurred for every test. Similarly, the auditory input produced a significant improvement for all tests except closed-set vowel recognition. The tactile input produced scores that were significantly greater than chance in isolation, but combined less effectively with the other modalities. The addition of the tactile input did produce significant improvements for vowel recognition in the auditory-tactile condition, for consonant recognition in the auditory-tactile and visual-tactile conditions, and in open-set word recognition in the visual-tactile condition. Information transmission analysis of the features of vowels and consonants indicated that the information from auditory and visual inputs were integrated much more effectively than information from the tactile input. The less effective combination might be due to lack of training with the tactile input, or to more fundamental limitations in the processing of multimodal stimuli.
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    Speech feature recognition by profoundly deaf children using the University of Melbourne multichannel electrotactile aid [Abstract]
    Alcantara, Joseph I. ; Whitford, Lesley A. ; Blamey, Peter J. ; Cowan, Robert S. C. ; Clark, Graeme M. ( 1989)
    Abstract not available due to copyright.
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    Preliminary evaluation of a wearable multichannel electrotactile speech processor [Abstract]
    Cowan, R. S. C. ; Blamey, P. J. ; Alcantara, J. I. ; Whitford, L. W. ; Clark, Graeme M. ( 1988)
    Speech discrimination testing, using both open-and closed-set materials was carried out with four severely-to-profoundly hearing impaired adults. and seven normally hearing subjects, to assess performance of a wearable eight-channel electrotactile aid (Tickle Talker). The device consisted of a handset composed of nine electrodes, a stimulator-unit, and a speech processor and input microphone. Eight small electrodes were located over the digital nerve bundles on each side of the four fingers of one hand, and a larger common electrode was placed on the wrist. Subjects perceived eight separate channels of information, each corresponding to a stimulus on one side of one finger. The speech processor provided estimates of second formant frequency, fundamental frequency and amplitude of the speech waveform. These features were coded as electrode position, pulse rate and pulse width respectively. This processing strategy (FOF2AO) is similar to that used in an earlier model of the Cochlear Pty. Ltd. cochlear implant.
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    Preliminary evaluation of a multichannel electrotactile speech processor
    Cowan, R. S. C. ; Alcantara, J. I. ; Blamey, P. J. ; Clark, Graeme M. ( 1988)
    Abstract not available due to copyright.
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    Phonemic information transmitted by a multichannel electrotactile speech processor
    Blamey, P. J. ; Cowan, R. S. C. ; Alcantara, J. I. ; Clark, Graeme M. ( 1988)
    A wearable electrotactile speech processor was evaluated in a study with seven normally hearing and four hearing-impaired subjects. The processor estimated the fundamental frequency, the second-formant frequency, and amplitude of the acoustic speech signal. These parameters were presented as a pattern of electrical pulses applied to eight electrodes positioned over the digital nerve bundles on one hand. The device was shown to provide useful information for the recognition of phonemes in closed sets of words using tactile information alone. The device also supplemented lipreading to improve the recognition of open-set words. The recognition of duration and first-and second-formant frequencies of vowels and the recognition of voicing and manner of consonants were improved over recognition with lipreading alone. Recognition of final consonants was improved more than recognition of initial consonants. These results indicate that the device may be useful to both severely and profoundly hearing-impaired people.
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    Evaluation of training strategies with an electrotactile speech processor [Abstract]
    Alcantara, J. I. ; Cowan, R. S. ; Blamey, P. J. ; Whitford, L. W. ; Clark, Graeme M. ( 1988)
    During 1986, seven normally-hearing subjects were trained in the use of an electrotactile speech processor ("Tickle Talker"). Two training methods were used: (a) a combined strategy. in which a variety of training materials ranging from analytic to synthetic level were employed; and (b) a synthetic alone training strategy, in which only synthetic level training materials were used. All seven subjects received 70 hours of training, 35 hours in each training strategy. Subjects were evaluated in the tactile-lipreading (TL) and lipreading alone (L) conditions at: (I) 0 hours training; (2) 35 hours training; and (3) after 70 hours of training. An evaluation test battery was constructed which contained both closed-set and open-set materials. Results indicated differences in performance on the evaluation tests which were dependent upon the training strategy. The differences in performance were greater in some evaluation tests than others. Subsequently; seven severe-profoundly hearing-impaired children (aged 7-11) have been fitted with the Tickle Talker and are presently participating in an ongoing training programme. Evaluation of their performance will help to assess the suitability of the device for young children.
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    Interim results of open-set speech discrimination with a wearable multichannel electrotactile speech processor
    Cowan, R. S. C. ; Alcantara, J. I. ; Blamey, P. J. ; Clark, Graeme M. ( 1987)
    Abstract not available due to copyright.