Graeme Clark Collection
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ItemA frequency importance function for a new monosyllabic word test( 1998)A frequency importance function, characterising the relative contribution of different frequency bands to speech intelligibility, was determined for a CNC monosyllabic word test designed for Australian usage at the University of Melbourne. The importance function was derived from the phoneme scores of 12 normally-hearing listeners who were tested under various conditions of low-and high-pass filtering presented at signal-to-noise ratios of -8 to +6 dB, using noise which was shaped across frequency 10 match the speech spectrum. The importance function showed a dominant peak at approximately 2000 Hz, which is consistent with previously published word test importance functions. The word test, along with the importance function, will be useful in advanced hearing-aid fitting procedures and research aimed at improving speech perception.
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ItemA modification of play audiometry to assess speech discrimination ability in severe-profoundly deaf 2- to 4-year-old children( 1998)Objective: The aim was to develop an assessment procedure that was independent of language and speech production ability, to test speech feature discrimination severe-profoundly deaf children 2 to 4 yr of age. Design: The procedure being trialled was adapted from existing procedures. The child was required to respond with a game-like motor response to a “change” in a speech stimulus that was being presented repeatedly through a speaker. The change occurred at randomly determined times, and false alarm responses were measured during the waiting periods (while the child waited for the change). Two- to four-yr-old normally hearing children and hearing-impaired children using hearing aids and a group of 4-yr-old hearing-impaired children using cochlear implants were assessed on the task. Results: More than 82% of the 3- and 4-yr-old normally hearing and hearing-impaired children were able to complete the testing for the eight speech sound contrasts within three 20 minute sessions. Fifty percent of the 2-yr-old normally hearing and hearing-impaired children were able to condition and complete the task. All of the normally hearing children who completed the task successfully discriminated all speech sound contrasts. The performance of the hearing-impaired children using hearing aids was influenced by the degree of hearing loss and the type of speech contrast being tested. Similarly, the average performance of the children using cochlear implants was better for easier contrasts such as /ba/bi/ with contrasting vowel formant cues. Conclusions: This procedure has potential for use as a reliable clinical and research tool for assessing the development of auditory discrimination ability in 2- to 4-yr-old severe-profoundly deaf children.
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ItemA comparison of Tactaid II+ and Tactaid 7 use by adults with a profound hearing impairment( 1999)Objective: To evaluate and compare use of the Tactaid II+ and the Tactaid 7, in terms of speech perception, by adults with a hearing impairment. Design: Eight adults used one device daily for approximately 10 wk and attended seven training sessions. Performance was measured with tests of phonetic contrast perception, closed-set vowel and consonant identification, word and phoneme recognition in monosyllabic word lists, word recognition in sentences and speechtracking rate. A questionnaire was also administered. The protocol was repeated with the alternative device. Results: With each device, the group discriminated most phonetic contrasts at better-than-chance levels and demonstrated somewhat enhanced visual or auditory-visual perception when measured in terms of vowel identification, monosyllabic word recognition and speechtracking rate. An increase in speechtracking rate was also demonstrated for some individuals. Subjects generally reported little subjective improvement in speech perception and production, but were satisfied with the physical attributes of each device. Five of six subjects preferred the Tactaid 7. Conclusions: The Tactaid II+ and the Tactaid 7 provided suprasegmental and segmental information, enabling the group to discriminate phonetic contrasts and improve their perception of some speech materials. No consistent advantage was found for either device, thought most subjects preferred the Tactaid 7. Alternatives likely to provide a greater benefit to communication should be considered before Tactaid fitting.