Dear colleagues,
Most oto-acoustic emissions (OAEs) appear to differ fundamentally from the reflection of electric signals at the end of coaxial cables. "AFAIK", the group delays of SFOAEs (stimulus-frequency OAEs) agree with the hypothesis that they are generated by outer hair cells (OHCs) in the basal-slope zone of the "active" (low-sound-pressure-level, healthy-cochlea) excitation peak of the sine-tone wave. These OHCs feed mechanical energy into the apically directed travelling wave (TW); some of that energy generates a basally directed TW, and so an OAE. DPOAEs (distortion-product OAEs, especially "low-side" ones, frequency f_DP = 2f_1 - f_2, where f_2 > f_1), on the other hand, have been found to have two distinct sources. The first source is the overlap region of the two excitation peaks of the two sine-tone waves with frequencies of f_1 and f_2. The second DPOAE source has been claimed to be the reflection of the cochlear TW travelling from the generation place to the (more apical) best place of that f_DP wave. Question: Is it possible that this second DPOAE is not due to a coaxial-cable-like reflection either, but is generated (similarly to the mentioned SFOAEs) by OHCs which feed energy into the apically directed f_DP wave?
Reinhart Frosch,
CH-5200 Brugg.
reinifrosch@xxxxxxxxxx .