Second Biennial Hearing Aid Research and Development Conference
September 22-24, 1997
National Institutes of Health
Hearing Problems of the Elderly Hearing Aid User
City University of New York and Balaji Oruganti, Lexington Center
The aging process is typically accompanied by more hearing difficulties than can be accounted for solely on the basis of peripheral hearing loss. The goal of the present study was to test the hypothesis that the discrepancy can be accounted for by increased context dependence and decreased channel capacity. Tests of sentence repetition were administered to 31 subjects, of whom 8 were ìyoungerî (aged 20 to 50 years), and 23 were ìolderî (aged 60 to 90 years). Among the older subjects approximately 6 had three-frequency average thresholds of 20 dBHL or less. The rest had various degree of mild or moderate hearing loss. Test materials were presented under headphones to the right ear at most comfortable listening level. These materials consisted of: a) meaningful sentences in quiet and in noise (speech-shaped, s/n ratio 5 dB), b) nonsense sentences (semantically anomalous) in quiet and noise, and c) pairs of meaningful sentences spoken simultaneously by the same talker. Subjects were asked to repeat what they heard. In the case of sentence pairs, they were asked to repeat both sentences in any order. Scores were the percentage of words correctly repeated. As a group, the older subjects performed less well than the younger subjects. When expressed in terms of a k-factor for aging (equivalent to a proficiency factor in Articulation Index theory), the age penalty was only a little higher in noise than in quiet and was no different for real and nonsense sentences. Moreover, the value for the first sentence repeated of the pairs was similar to that for simple noise masking. These findings do not support the hypothesis of context-dependence, nor do they implicate competing messages as a complicating factor. In contrast, the age penalty for the second sentence repeated of the pairs was considerably higher than for any other task. This finding supports the reduced channel-capacity theory but is also consistent with the theory that short-term or working memory is impaired in elderly subjects. In stepwise multiple regression analysis, performance on all but one of the measures was adequately explained by auditory threshold in the range 2 to 8 kHz. The exception was the second sentence repeated in the pairs, for which age was the best predictor. This finding further supports the notion that the simultaneous sentence task is effective in probing those speech perception problems of the elderly that go beyond the effects of deteriorating peripheral function.
[Research supported by NIDRR]
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