Similarities and differences in distortion-product otoacoustic emissions among four FDA-approved devices.

Similarities and differences in distortion-product otoacoustic emissions (DPOAEs) among four Food and Drug Administration (FDA) approved devices were assessed quantitatively. DPOAEs were recorded from 42 adult subjects (84 ears) ranging in age from 19 to 40 years. All subjects had hearing thresholds of 20 dB HL or better for the test frequencies from 0.25 to 8.0 kHz and normal acoustic immittance findings. DPOAEs were collected in a quiet non-sound-treated room. DPOAE measurement parameters included an f2/f1 ratio of approximately 1.2, with f1 at 65 dB SPL (L1) and f2 at 55 dB SPL (L2). There were no significant differences in the mean emissions levels among the four devices. This investigation showed that validity criteria, pass criteria, and strategies for DPOAE measurements interact to produce varying pass and refer results. However, when DPOAEs are obtained with consistent validity criteria, pass criteria, and strategies for measurement, the results are remarkably consistent.

Aging and contralateral suppression effects on transient evoked otoacoustic emissions.

Transient evoked otoacoustic emissions (TEOAEs) were recorded in 30 normal-hearing subjects to nonlinear clicks while continuous contralateral broadband noise (CBBN) was presented at 40, 50, 60, and 70 dB HL. Thirty subjects between 20 and 79 years were divided system-atically into six-decade age groups, five subjects per group. All subjects in each group had hearing thresholds of 20 dB HL or better for the test frequencies from 0.25 to 8.0 kHz and normal acoustic immittance findings. The results provide evidence that contralateral suppression at varying levels of CBBN is interactive with age. Except for subjects in the age ranges between 60 and 69 and 70 and 79 years of age, an increase in CBBN from 40 to 70 dB in 10-dB steps resulted in an average increase in suppression from about 0.5 to 3.5 dB SPL. In addition, the contralateral suppression at 60 and 70 dB HL was significantly greater for subjects between 20 and 59 years of age than for subjects between 60 and 79 years of age.

Effects of repetition rate, phase, and frequency on the auditory brainstem response in neonates and adults.

This study evaluated the effects of stimulus repetition rate, phase, and frequency on the auditory brainstem response (ABR) in normal-hearing neonates and adults. In both neonates and adults, the results clearly showed large ABR wave V latency differences between condensation and rarefaction for low-frequency stimuli. Phase dependent latency effects are believed to be a result of the phase-sensitive low-frequency neurons. Increasing stimulus repetition rate produced greater wave V latency shift in neonates than in adults. The consequences of rate changes were independent of stimulus phase and frequency.

Rate, frequency, and intensity effects on early auditory evoked potentials and binaural interaction component in humans.

The binaural interaction component (BIC) of the auditory brainstem response (ABR) and BIC of the frequency-following response (FFR) to tonal stimuli were studied in normal-hearing adults. The ABR and BIC latencies from all subjects were consistently shorter to the click-like sound than to the 2.0 kHz tone burst. Increasing stimulus presentation rate produced longer latencies and diminished amplitudes of ABR and BIC waveforms. The consequences of rate changes were independent of sound level. The FFR and BIC latencies to low-frequency tone bursts (0.5 and 1.0 kHz) were minimally affected by rate, but their amplitudes were modified. The results are consistent with and reflective of the functional characteristics of lower brainstem auditory neurons. The results provide evidence that the BIC to tones is differentially sensitive to the rate, frequency, and intensity of sounds other than clicks.