Extended low-frequency phase of the distortion-product otoacoustic emission in human newborns

At constant f 2 / f 1 ratios, the phase of the nonlinear distortion component of the 2 f 1 − f 2 distortion-product otoacoustic emission (DPOAE) has a steep low-frequency segment and a flat high-frequency segment in adults and newborns. In adults, recent work found that a third segment characterizes the phase at even lower frequencies. The present study tests whether the same is true of the newborn DPOAE phase. Newborn and adult phase curves are generally similar. However, as previously reported, phase-gradient delays at mid frequencies (the region of steepest phase slope) are 50% longer in newborns.