The effect of aging on discrimination of filtered speech was examined. There are some words, which are increasingly difficult to discriminate as the age progresses, among the filtered speech words list, and thus the effect of the aging of the examinees is one of the influential factors for the articulation scoring. Four kinds of filters, 2000Hz low pass, 1700Hz low pass, 1200Hz low pass and 850-1700Hz band pass, were used to distort 20 speech words list, which were recognized to bring about less discrimination as age progresses.
Thus made speech words list was heared by the examines, aging from 20 to 74 years old, monoaurally at the pure tone threshold according to the corresponding age, and the articulation score of discrimination was compiled for each age groups at 5 years of intervals.
The articulation score of discrimination for some words list was 76% in average in the twentieth, which fell with age reaching 12% in average in more than 70 years old population. Distinct correlation between the articulation score of discrimination and age was observed (correlation coefficient, 0.879), and there was no sex difference in any age populations.
The test speech words list was applied to four groups of young subjects, aging from 20 to 34 years old, having elevated pure tone threshold, (500Hz+1000Hz+2000Hz/3) (<10dB, 15-25dB, 35-45dB, >60dB).
There was less effect of elevation of the pure tone threshold on the articulation score of the filtered speech up to about 20dB.,
The pure tone discrimination of the young subject, showing elevated threshold, was almost the same as that in the aged, more than 60 years old in the articular score, and thus lowering of the articular score in 40-50dB correcting for the pure tone threshold was estimated in the aged subjects at the post-labyrinth.
The age dependent change in the auditory system may be gradually and continuously changed after 20 years of age, from the inner ear to the central nerve and from the low frequency to high frequency regions both in male and in female. Modification of noise and arterial screlosis would reflect to the audiogram in the aged subjects.
