Distortion Product Otoacoustic Emissions: Input-output Functions for Primary-tone Pairs at 1000, 2000 and 4000 Hz in Normal-hearing Females

Because little information is available on the normal characteristics of input-output DPOAE functions, we measured (1) group slopes at f2 = 1000, 2000 and 4000 Hz for low-level (40-50 dB SPL), moderatelevel (50-65 dB SPL), and high-level stimuli (65-75 dB SPL); (2) individual slopes for each frequency and intensity level segment; (3) test-retest reliability of slopes for each frequency and intensity level segment; and (4) the proportion of subjects with various input-output function shapes. Fifty normal-hearing female subjects were tested. The results showed that (1) the intersubject slope variability among subjects was large (standard deviations were 0.5); (2) the lowlevel segments exhibited steeper slopes (0.67-0.82) than the high-level segments (-0.03 - 0.43), and the moderate-level segments showed intermediate slopes (0.39 - 0.64); and (3) slopes for the low-level and moderate-level segments tended to increase as frequency increased from 1000 Hz (slope = 0.53) to 4000 Hz (slope = 0.73). Approximately two thirds of the DPOAE input-output functions were the Linear-Plateau type (41%) or the Linear type (26%). The Rollover type of function also was fairly common and observed in 16% of the cases.