Modeling the combined effects of basilar membrane nonlinearity and roughness on stimulus frequency otoacoustic emission fine structure

A theoretical framework for describing the effects of nonlinear reflection on otoacoustic emission fine structure is presented. The following models o f cochlear reflection are analyzed: weak nonlinearity, distributed roughnes s, and a combination of weak nonlinearity and distributed roughness. In par ticular, these models are examined in the context of stimulus frequency oto acoustic emissions (SFOAEs). In agreement with previous studies, it is conc luded that only linear cochlear reflection can explain the underlying prope rties of cochlear fine structures. However, it is shown that nonlinearity c an unexpectedly, in some cases, significantly modify the level and phase be haviors of the otoacoustic emission fine structure, and actually enhance th e pattern of fine structures observed. The implications of these results on the stimulus level dependence of SFOAE fine structure are also explored. ( C) 2000 Acoustical Society of America. [S0001-4966(00)01012-2].