FIG. 3.

DP-gram difference plots showing that the average DPOAE adaptation in the alert rabbit elicited by either 55 -(A) or 75-dB SPL (B) primaries was likely composed of both a presumed olivocochlear efferent reflex (MOC-R, open circles) plus a middle-ear muscle reflex (MEM-R, filled circles) component. The presumed “MEM-R” contribution to DPOAE adaptation measured with an f₁ primary-tone constancy test (see text) increased with the higher 75-dB SPL sound pressure levels, yet was still detectable at 55 dB SPL, which is below the reported acoustic threshold for the MEM response in alert rabbits (see text). The bold dashed line at “0” on the ordinate represents a “no change” outcome in which the level of f₁ stayed at a constant level between the monaural baseline and, in this case, the delayed-binaural condition.