Distortion product otoacoustic emission (DPOAE) was investigated in 10 persons with bilateral normalhearing and in 10 with unilateral cochlear deafness. DPOAE was recorded by an Otodynamic Analyser ILO92 (Version 1.31) which was recently developed by Kemp. The F2/F1ratio was fixed between 1.18 and 1.20 and the DP level at 2F1-F2was investigated at 14 points of F1between 598Hz and 5273Hz and F2between 708Hz and 6299Hz. The stimulus intensity of primaries was fixed to 70dBSPL at F1and 60dBSPL at F2, respectively. The distortion product-gram (DP-gram) was drawn from the DP levels at 14 individual F2points.
The results obtained were as follows;
1) DPOAE with high level was obtained even in high frequency areas above 4kHz in all normal-hearing ears.
2) There was a relatively large intersubject variance in the DP level at 14 individual F2points and also in the configuration of DP-gram in normal-hearing ears.
3) When the averaged DP-gram was drawn from the individual DP-grams in 20 normal-hearing ears, the mean DP level was the highest around 5kHz. The mean DP level below 1kHz was found to be low.
4) The interaural defference of DP levels at 14 individual F2points and that of the configuration of DP-gram was found to be minimal in the persons with bilateral normal-hearing.
5) The short-term reproducibility of DP levels at 14 individual F2points and that of the configuration of DP-gram in consecutive repeated tests was excellent in normal-hearing ears.
6) DPOAE could not be elicited in the frequency areas with 50dB or more of pure-tone hearing level in cochlear deafness.
7) When the relationship between pure-tone audiogram and DP-gram was analysed in cochlear deafness, the excellent correspondence with frequency specificity was found between them.
8) Based upon these results, it was concluded that DPOAE could be a very useful clinical tool for objective investigation of the frequency-specific cochlear function in the ears with sensorineural hearing loss.
