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active travelling waves, DPOAEs and the Cochlea Amp.

Hello all,

I can easily see the stapes driven passive travelling wave. I am still 
at a loss for the second travelling wave ...

Current theory for explaining the generation of DPOAEs requires the 
Cochlea Amplifier.

I am writing this summary to set the scene ... it is the current active
travelling wave point of view ...

Those models which rely on Travelling Wave activity propose the following 
[1] :
The distributed travelling wave amp. amplifies a signal which is 
generated and this signal travels in two directions. One apical going 
wave reflects off the lower frequency (2f1-f2) DP resonant location on 
the BM. The other wave reflects off the oval window. This oval window 
reflection generates the DPOAE in the middle ear.

In the above treatment, the two frequencies f1 and f2 reside between the 
oval window and the 2f1-f2 DP frequency.

Now please consider the 2f2-f1 DPOAE.

Interestingly, the 2f1-f2 and 2f2-f1 DPs have similar nature - although 
the 2f2-f1 DP is of a lower level. They both have a band pass nature 
with respect to f2 frequency glide [2] ... and so on ....

My question to the list is :

Can anyone please explain how this travelling wave point of view can 
generate a DPOAE when the DP is the 2f2-f1 DP ?
In this case, the DP sits between the oval window and the probe 
frequencies f1 and f2.

If you can explain that, then please also explain what happens to the 
apical going travelling wave ???


[1] @ARTICLE{shera:2005,
  author = {Shera, C.A. and Tubis, A. and Talmadge, C.L.},
  title = {{Coherent reflection in a two-dimensional cochlea: Short-wave 
	long-wave scattering in the generation of reflection-source 
  journal = {The Journal of the Acoustical Society of America},
  year = {2005},
  volume = {118},
  pages = {287},
  publisher = {ASA}

[2] @ARTICLE{fahey:2006,
  author = {Fahey, PF and Stagner, BB and Martin, GK},
  title = {{Mechanism for bandpass frequency characteristic in 
distortion product
	otoacoustic emission generation}},
  journal = {The Journal of the Acoustical Society of America},
  year = {2006},
  volume = {119},
  pages = {991},
  publisher = {ASA}


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