Preliminary descriptions of transient-evoked and distortion-product otoacoustic emissions from graduates of an intensive care nursery.

Transient-evoked (TEOAE) and distortion-product otoacoustic emissions (DPOAE) were measured in 51 graduates of an intensive care nursery and compared to data obtained from 80 normal-hearing children and adults. All infants had click-evoked auditory brainstem responses (ABR) at 30 dB nHL or less while the older subjects had pure-tone thresholds of 20 dB HL or less for octave frequencies from 250 to 8000 Hz. OAE data were collected using commercially available devices. All data were analyzed in terms of emission amplitude, emission-to-noise ratio, and response reproducibility as a function of frequency. DPOAEs were measured at three points per octave between f2 frequencies of approximately 500 and 8000 Hz. TEOAEs were elicited by clicks and were analyzed in both octave and 1/3-octave bands centered at frequencies from 500 to 4000 Hz, as well as in the broadband condition. In addition, stimulus amplitudes for the clicks used to elicit TEOAEs were analyzed within octave and 1/3-octave bands to determine whether any age-related differences in responses can be accounted for on the basis of stimulus differences. Both emission amplitude and noise amplitude were greater in neonates than adults, although there was variability across frequency. Emission-to-noise ratio and response reproducibility were more similar between groups. For TEOAEs, high-frequency emission-to-noise ratios were larger in neonates compared to older subjects, while the reverse was true in the lower frequencies. Less obvious frequency effects were observed for DPOAEs. These findings are discussed in relation to the potential use of OAEs as screening measures for neonatal hearing loss.