While probably running the risk of being prematurely philosophical the authors have attempted to present a unified point of view which attempts to broadly draw on (much of) the experimental cochlear data presently available. Many other important and relevant factors have not been mentioned in this discussion such as how the non linear damping might arise, how pressure and displacement might jointly interact on the cilia, or how the outer hair cells enter into the global picture. The outer hair cells are coupled to the efferent system and COCB stimulation (Ref. E11) (stimulation of the outer hair cells through the efferent system) also gives rise to broadened tuning about CF in a manner very similar (as best we know) to the nonlinear level dependent mechanical damping (Weiderhold, E11, 1970). This experimental fact seems to be an important clue toward an understanding of the cochlear nonlinearity. If the mechanical system is nonlinear, as the authors presently believe, a further interesting question remains. How could nonlinear damping have affected Rhode's mechanical measurements? It was necessary for Rhode to drive the cochlea with a wide range of input levels in order to measure its output frequency response, due to the limited dynamic range of the measurement system. If each of the various input levels gave rise to a different BM damping, no linear model would be successful in matching the measurements with one value (the linear case) of damping. This was the argument that Allen and Sondhi (A3, 1979) found necessary in attempting a match model response to Rhode's magnitude and phase data using the linear time domain two-dimensional model. Wide band noise cross correlation measurement methods [such as 'rev-cor,' de Boer, (E2, 3, 1968, 1973; Evans E5, 1975] seem to be a convenient means by which one might skirt this signal dependent damping problem since they use a stationary signal to measure the signal dependent system 'frequency response' of the cochlear filters, unlike the 'nonstationary' pure tone stimuli used by Rhode.
|Original language||English (US)|
|Number of pages||16|
|Issue number||Suppl. 9|
|State||Published - 1979|
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