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DPOAE L/P maps obtained with and without an IT placed below . The residual map in (e) demonstrates that DPOAE components can be extracted near that have vertical-phase banding properties in (f) (arrows). Red/gray dashed line in (h) demonstrates that these emissions have the expected steep phase gradients consistent with a DPOAE-reflection component. However, in the presence of the IT, large DPOAE components remain (c) associated with similar vertical banding (d) and phase gradients as indicated by the blue/gray line in (i). Black dashed lines on the DPOAE L/P maps indicate ratios where data were extracted for the plots in (g) and (h) (see text for complete details of this and Fig. 2).
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DPOAE maps obtained with and without an IT placed 0.33 oct above . The residual map in (e) demonstrates that by placing the IT above , large DPOAE components can be extracted that have phase properties of both distortion and reflection emissions, depending upon the ratio (f). Shallow and steep phase gradients associated with these two components were confirmed by extracting the phase curves at a wide ratio in (h), and at a narrow ratio in (i) (dashed red/gray lines). In (d), almost all of the narrow -ratio vertical-phase banding was removed by the IT for the narrow ratio DPOAE, and similarly for the DPOAE, suggesting that both of these reflectionlike components originate in regions of the cochlea that are basal to the IT place.
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Distortion product otoacoustic emission (DPOAE) level/phase maps were collected in humans with and without an interference tone (IT) near the DPOAE frequency place at primary-tone levels of SPL. A DPOAE component with the expected steep phase gradient could be extracted at , however, considerable vertical-phase banding, presumably indicative of reflection emissions, remained. An IT placed 0.33 oct above removed most of this banding, revealing DPOAE components originating basal to the IT frequency place. These findings suggest that the commonly accepted two-source model of DPOAE generation may need to be qualified when higher primary-tone levels are utilized.
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