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

Abstract

At constant ratios, the phase of the nonlinear distortion component of the 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.

Swept Along: Measuring Otoacoustic Emissions Using Continuously Varying Stimuli

“…But Fig. 5 suggests that employing faster rates at higher frequencies (i.e., using variable sweep rates that parallel the BM group velocity curve) might be more natural, perhaps helping to compensate for place-specific changes in cochlear mechanics or OAE generation, such as the well-known differences in scaling behavior between the apical and basal regions of the cochlea [ 31 – 35 ]. Reducing the sweep rate at low frequencies can also be a useful tool for countering the frequency dependence of contaminating noise sources.…”

“…Swept-tone methods have been applied in a diverse array of ears, including both the normal and the hearing impaired [ 67 ], the latter from a variety of etiologies [ 68 ]; in humans to study the maturation and aging of the peripheral auditory system in subjects ranging from newborns to the elderly [ 69 – 73 ]; in young adults to study the breaking of scaling symmetry [ 32 , 33 , 35 ]; and in comparative studies involving other animals, including mice, gerbils, anole lizards, barn owls, and clouded leopards [ 74 , 75 ]. The swept-tone method also provides a valuable tool for probing cochlear mechanics, especially the complex temporal interactions between nonlinearity and dispersion [ 37 , 76 ].…”