純音聴力検査における耳載せ形と耳覆い形イヤホンの比較 : 閾値の再現性と、正常耳の聴覚閾値レベル Comparison between supra- and circum-aural earphones in pure-tone audiometry : Test-retest variability and normal hearing threshold levels
It has become possible to use circum-aural earphone in clinical pure-tone audiometry because its reference equivalent threshold sound pressure levels were standardized recently. In this study, test-retest intra-subject variability in pure-tone audiometric threshold at seven frequencies with circum-aural (HDA-200) and traditional supra-aural (AD-02) earphones was investigated.<BR>After the first test, each earphone was removed and replaced for the second test. Equivalence of thresholds with the above two earphones was also investigated.<BR>At 12 Hz and 250 Hz, test-retest variability with circumaural earphone was significantly smaller than that with supra-aural earphone. From this result, it was expected that the use of circum-aural earphone could improve accuracy of hearing tests like glycerol test in which the presence of small threshold change must be evaluated at low frequencies.<BR>The mean hearing threshold levels of otologically normal subjects aged between 18 and 25 years were within 2.1 dB at every frequency with circum-aural earphone, whereas they were more than 5 dB at 125 Hz and 250 Hz with supra-aural earphone, as previously reported. There were significant threshold differences at low frequencies of the same ear between two earphones. This result indicates that current calibration method of supra-aural earphone neglecting the influence of sound leakage from the gap between earphone and pinna should be modified.
- Otology Japan
Otology Japan 17(3), 209-213, 2007-07-25
THE JAPAN OTOLOGICAL SOCIETY