DPOAE component estimates and their relationship to hearing thresholds.

Distortion product otoacoustic emissions (DPOAEs) recorded in the ear canal are a composite or vector sum of two underlying components. The relationship between hearing thresholds and DPOAE-component level, rather than composite level, has been of recent interest. Two different signal-processing methods, inverse fast Fourier transform (IFFT) with time-windowing and low-pass filtering, were used to obtain estimates of the levels of the two components. Component estimates were then correlated to behavioral thresholds. Improvement in the strength of the correlation was not significant over that of the composite. While the signal processing methods were found to yield similar estimates of the generation component, application of the IFFT with time-windowing method was more complex due to the overlap of the components in the time domain. This time domain variability was observed both within and between subjects. These results highlight the complexities of DPOAE generation and the related difficulties of component separation.