Abstract
The evoked otoacoustic emission (e-OAE) against the stimulus sounds at 500 Hz was investigated in 72 ears. The subjects consisted of 57 ears with normal hearing and 15 ears with cochlear deafness. The stimulus sounds were tonebursts with 2 ms rise/fall time and 6 ms total duration. The responses 30 ms after the stimulus onset were averaged 500 times with the band pass between 200 Hz and 1 kHz.
The results obtained were as follows;
1) The clear e-OAEs were obtained in 70 ears out of 72 (97.2%) and the e-OAE pseudothreshold was able to be analyzed in 64 ears (88.9%).
2) The frequency of e-OAE almost corresponded to the stimulus frequency in either normal hearing ears or cochlear deafness.
3) In normal hearing ears, the e-OAE pseudothreshold was distributed between-15 dB (nHL) and 30 dB and the mean e-OAE pseudothreshold was 7.2 dB.
The intersubject variance of e-OAE pseudothreshold was relatively large, while the interaural difference of e-OAE pseudothreshold was within 5 dB in 90.0% of the subjects.
4) In cochlear deafness, the e-OAE pseudothreshold was distributed between 35 dB and 55 dB and the mean e-OAE pseudothreshold was 42.9 dB which was remarkably higher than that in normal hearing ears.
5) A positive correlation was found between e-OAE pseudothreshold elicited by 500 Hz tonebursts and pure-tone hearing level at 500 Hz.
6) When the configuration of emission cochleogram between 500 Hz and 4 kHz and that of pure-tone audiogram were compared in impaired side of cochlear deafness, an excellent correspondence was found between them considering the fact that the e-OAE pseudothreshold is elevated at high frequencies even in normal hearing ears.
Based upon these results, it was concluded that the recording of e-OAE elicited by 500 Hz tonebursts enabled us to analyze the function of cochlear micromechanics of a wider frequency range.
