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Speech intelligibility of non-hearing-impaired adults as assessed by a closed logatome test
18 April 2018 (online)
Logatomes, non-sensical combinations of consonants and vowels, are suitable for a precise capture and analysis of individual phonemes as fundamental modules of speech in audiometric diagnostic. We analyzed the slope of the discrimination function at the speech reception threshold (SRT) and the test-retest-reliability in a prospective evaluation of a logatome test.
Intensity-variated and randomized logatomes were presented in the form of consonant-vowel-consonant to 25 non-hearing-impaired adults. The measurements were performed in a free field setting and were repeated once after a two-week interval. The subjects were requested to repeat the heard logatome in a closed-response test of 10 items per sound item on a touchscreen.
The slope of the mean discrimination function (MDF) at the SRT was 4%/dB. However, the MDF slope was steeper for the initial consonant than for the final one.
The differences of the test and retest results at the SRT showed a standard deviation of 13% for consonants. These differences were normally distributed. There was no significant difference in logatome intelligibility between test and retest.
The slope of the discrimination function (DF) at the SRT appears shallow but is comparable to established word tests.
However, the shape of the DF differs strongly depending on its sound and position:
Vowels are understood the best while the intelligibility of consonants in the initial sound of the logatome improves more from an elevation of the sound pressure level than consonants in the final sound.
Finally, there is no evidence of a learning effect in the retest, which emphasizes the low redundancy of the speech material and makes this speech test an attractive complementary option to routine diagnostic.