Modeling the temporal behavior of distortion product otoacoustic emissions

The temporal behavior of the 2f(1) - f(2) distortion product otoacoustic em ission is theoretically investigated for the case in which the lower freque ncy (f(1)) primary tone is on continuously, and the higher frequency (f(2)) one is pulsed on and off [e.g., Talmadge et al., J. Acoust. Sec. Am. 105, 275-292 (1999)]. On physical grounds, this behavior is expected to be chara cterized by various group delays associated with the propagation of (1) the f(2) cochlear primary wave between the cochlear base and the primary disto rtion product generation region around <(x)over cap(2)> (the f(2) tonotopic place), and (2) the 2f(1) - f(2) cochlear distortion product (DP) waves be tween the cochlear base, the primary generation region of the distortion pr oduct, and the region around the 2f(1) - f(2) tonotopic place where the gen erated apical moving DP wave is reflected toward the cochlear base [e.g., T almadge et al., J. Acoust. Soc. Am. 104, 1517-1543 (1998)]. An approximate analytic expression is obtained for this behavior from the analysis of the Fourier integral representation of the auditory peripheral response to the primary stimuli. This expression also approximately describes the transient build-up of the components of different latencies in terms of the damping properties of the cochlear partition. It is shown that considerable caution must be applied in attempting to relate phase derivatives of the distortio n product otoacoustic emissions for steady state stimuli and the physical t ime delays which are associated with the temporal behavior of a distortion product emission in the case of a pulsed primary. (C) 2000 Acoustical Socie ty of America. [S0001-4966(00)03503-7].