DPOAE Measurements at Frequency Fine Structure Before and After Contralateral Suppression

Abstract

The purpose of this study was to investigate distortion product otoacoustic emission (DPOAE) measurements before and after contralateral suppression at frequency fine structure. 8pts/octave DP-gram was measured at f2 frequencies ranging from 841 Hz to 8,000 Hz in fifty six ears of normal hearing adults with and without contralateral broad band noise (BBN) at 70 dB SPL. The data were analyzed depending on groups by gender, age(20's, 30's, and 40's+) and directions of the ear. Results showed the followings: (1) DPOAE amplitude was decreased significantly with presence of broad band noise, showing contralateral suppression. (2) At the frequency fine structure, change in DPOAE amplitude before and after suppression was significant. The great amplitude change was observed between 1,000 and 2,000 Hz for most participants. (3) Change in DPOAE amplitude before and after suppression was not significant depending on gender and age, but was significant depending on directions of the ear. (4) Change in DPOAE amplitude before and after suppression was significant for peak and dip frequencies. Also, change in DPOAE amplitude was mostly suppressed at the peak frequencies, however, change in DPOAE amplitude was varied at the dip frequencies. A larger inter-subject variability was observed in the dip frequencies. The results suggest that measuring DPOAE contralateral suppression at peak frequencies in DPOAE would improve efficiency of the auditory efferent system assessment.