The Variation in Otoacoustic Emission Data according to the Different Location of Probe / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: Microphones designed to measure otoacoustic emissions (OAEs) from the human ear canal typically sample the sound field in the canal some 15-20 mm away from the tympanic membrane. Discrepancies inevitably arise at high frequencies between the sound pressure at the tympanic membrane and at the entrance to the emission probe from sound reflected by the tympanic membrane due to incomplete absorption. A previous work on the ear canal acoustics suggests the emission probe underestimate the sound pressure level of the stimulus at the tympanic membrane by as much as 15-20 dB for the stimulus frequencies near 5-7 KHz. Materials and Method: This study checked the variation of transiently evoked otoacoustic emissions (TEOAEs) and distorsion product otoacoustic emissions (DPOAEs) for the situations of probe which were controlled by ear canal volume. RESULTS: All mean values on TEOAEs (stimulus level, echo response, reproducibility) significantly increased (p 0.05) as the ear canal volume decreased. The mean amplitude of DPOAEs significantly increased at 1.6, 2, 25, 3.2, 4 (F2 frequency) and the variation of the mean noise level was statistically significant at 1, 2, 4 KHz (F2 frequency). The mean signal to noise ratio on DPOAEs significantly increased at 1, 2, 3.2, 4, 6.3 KHz (F2 frequency). CONCLUSION: These results suggest that the reliability of measurements of otoacoustic emissions should be improved when the probe is located nearer to the tympanic membrane.

Test-Retest Differences and Assistive Function in Detecting Conductive Hearing Loss of lmpedance Audiometry

lmpedance audiometry requires physical modifications during the test, which might influence retest data. Therefore, in Order to interprete retest data meaningfully, the range of variation should be identified in each measure of impedence audiometry. The present study obtained data on the retest variation of peak pressure, acoustic reflex threshold, static compliance and earcanal volume in impedance audiometry. ln addition, the authors wanted to know whether or not impedance data would assist otolaryngologists in the detection of conductive hearing impairment. The variation of the retest data was not clinically nor statistically significant in the measurement except for those of ear canal volume. The data on ear canal volume also suggested that the ear canal increases in size during the teenage period and that male ear canals are larger than those of females in ears over 20 years of age. The impedance data assisted the otolaryngologist in the detection of conductive hearing impairment