An examination of gender differences in DPOAE phase delay measurements in normal-hearing human adults

This study examined gender differences in f 1- and f 2-sweep distortion product otoacoustic emission (DPOAE) phase delay measures in 60 normal-hearing human adults. Phase delay measures were obtained at six different f 2 frequencies ranging from 1.1 to 6.0 kHz ( f 2/ f 1 ratios were 1.1–1.3). Primary levels for f 2 were 45 and 50 dB SPL ( f 1 was 15 dB> f 2). Gender differences have been observed in normal-hearing human adults in both auditory brainstem response (ABR) and f 1-sweep DPOAE studies. Gender differences in delay have been attributed to differences in the average length of the cochlea, where female cochleas are 13% shorter than male cochleas. Previously, the authors have proposed that the f 1-sweep phase delay estimate is predominantly composed of a level-independent transport time to the site of DPOAE generation and a small proportion of the level and frequency-dependent filter build-up time. The f 2-sweep delay also contains the transport time, however, it is predominantly composed of the filter build-up time. Therefore, delay differences between stimulation paradigms are equal to a proportion of the filter build-up time. In this study, mean f 1- and f 2-sweep delays were significantly longer in male ears than female ears at 1.1 kHz (45 and 50 dB). At 50 dB, f 1-sweep phase delay measures were 18% longer in male ears (6.5 ms) than female ears (5.5 ms). Mean f 2-sweep delays were 23% longer in male ears (10.0 ms) than female ears (8.1 ms). This gender difference was not observed when the isolated filter build-up time was calculated from the DPOAE phase delay difference. These observations may therefore be attributed to a gender-related anatomical difference in cochlear length.