Abstract

The goal of this study was to determine the extent to which we could account for the variability seen in distortion product otoacoustic emissions (DPOAEs) among ears with normal hearing. Several factors were selected for investigation, including behavioral threshold (representing cochlear status), differences in middle-ear transmission characteristics either in the forward or the reverse direction, and differences in contributions from the distortion and reflection sources. These variables were assessed after optimizing stimulus parameters for individual ears at each frequency. A multiple-linear regression was completed to identify whether threshold, middle-ear transmission and source contribution, either individually or in combination, explained significant portions of variability in DPOAE responses. Behavioral threshold at the f2 frequency and behavioral-threshold squared at that same frequency accounted for the largest amount of variability in DPOAE level, compared to the other variables, even though these threshold-related predictors did not account for large amounts of variance. The combined model accounted for a significant, although small amount of variance in DPOAE level at five frequencies, or more than half of the frequencies studied. There still is a large amount of residual variability, even for those frequencies for which the model was able to account for significant amounts of variance. Possible sources of this variability may be a potential bias introduced by stimulus optimization, the small number of ears tested compared to previous studies, and calibration.