Influence of ultrahigh-frequency hearing thresholds on distortion-product otoacoustic emission levels at conventional frequencies.

This study examined the association between ultrahigh-frequency (UHF) hearing sensitivity and distortion-product otoacoustic emission (DPOAE) levels at conventional frequencies. Behavioral thresholds were measured from 2 through 16 kHz, and DPOAE levels were measured at discrete f2 frequencies between 2 through 8 kHz in 553 young normal-hearing adult male participants. A DPOAE frequency sweep was measured with primary stimulus levels of L1/L2 = 65/55 dB SPL and an f2/f1 of 1.2. Significant negative correlations, although weak, were found between UHF behavioral thresholds and DPOAE levels. As UHF behavioral thresholds worsened, DPOAE levels decreased at all frequencies. When the data were categorized into two groups, "better" and "worse" UHF behavioral thresholds, significant differences were apparent between the two groups for DPOAEs. Additionally, those with better UHF thresholds had better conventional thresholds compared to those in the worse UHF threshold group. The results of this age-restricted, large-sample-size study confirm and augment findings from earlier studies demonstrating that UHF hearing sensitivity has some influence on DPOAE measures at frequencies from 2 through 8 kHz with moderate stimulus levels. However, because those with better UHF thresholds also had better conventional thresholds and the significant correlations found were weak, this work supports the importance of UHF hearing testing in conjunction with otoacoustic emission measures to identify basal cochlear insults not evident from behavioral testing at conventional frequencies.

Repeatability of high-frequency distortion-product otoacoustic emissions in normal-hearing adults.

OBJECTIVES: Distortion-product otoacoustic emissions (DPOAEs) are repeatable over time at lower frequencies (8 kHz) for DPOAE level measurements. The average DPOAE level differences-between-trials for the higher and lower frequencies for the four different stimulus level conditions was 5.15 (SD = 4.40 dB) and 2.80 (SD = 2.70 dB) dB, respectively. Individual subject analysis revealed that high-frequency DPOAE levels varied no more than 10 dB for 87.5 and 83.1% of young adult subjects for the 70/55 and 60/50 dB SPL stimulus level conditions, respectively. For low frequencies, repeated DPOAE level variations were within +/-10 dB for 98.4 and 96% of young adult subjects for the 70/55 and 60/50 dB SPL stimulus level conditions, respectively. For DPOAE group delay, greater variability was noted at lower frequencies (