Subject: active travelling waves, DPOAEs and the Cochlea Amp. From: Matt Flax <flatmax@xxxxxxxx> Date: Fri, 5 Oct 2007 00:20:45 +1000 List-Archive:<http://lists.mcgill.ca/scripts/wa.exe?LIST=AUDITORY>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 ??? thanks Matt [1] @xxxxxxxx{shera:2005, author = {Shera, C.A. and Tubis, A. and Talmadge, C.L.}, title = {{Coherent reflection in a two-dimensional cochlea: Short-wave versus long-wave scattering in the generation of reflection-source otoacoustic emissions}}, journal = {The Journal of the Acoustical Society of America}, year = {2005}, volume = {118}, pages = {287}, publisher = {ASA} } [2] @xxxxxxxx{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} } thanks Matt -- http://www.flatmaxstudios.com/ http://www.flatmax.org Public Projects : http://sourceforge.net/search/?type_of_search=soft&words=mffm http://www.psysound.org