Demonstration of distributed distortion-product otoacoustic emission components using onset-latency techniques

An oversimplified notion is that DPOAEs originate from a restricted region on the basilar membrane (BM). In actuality, DPOAEs are a distributed process involving the interaction of many wavelets, most likely generated over a broad region at, and basal to the overlap place of the primary tones. In the present study, DPOAEs were measured in rabbits as time waveforms by using phase rotation to cancel all components in the final average, except the 2f1-f2 DPOAE. At times, f2 was turned off for 6 ms producing a gap so that the DPOAE was no longer generated. These procedures allowed the DPOAE onset as well as the decay during the gap to be observed in the time domain. Results showed that complexities emerged near the onset of the DPOAE time waveform as the f2/f1 ratio decreased, and at the beginning of the gap when f2 was turned off. Such complexities were unaffected by interference tones (ITs) near the DPOAE. However, these complexities were removed by ITs presented above f2, which can be explained by the interactions of distributed DPOAE components with different phase relationships.