Properties of a nonlinear version of the stimulus-frequency otoacoustic emission

Abstract

A procedure for extracting the nonlinear component of the stimulus-frequency otoacoustic emission ͑SFOAE͒ is described. This nSFOAE measures the amount by which the cochlear response deviates from linear additivity when the input stimulus is doubled in amplitude. When a 4.0-kHz tone was presented alone, the magnitude of the nSFOAE response remained essentially constant throughout the 400-ms duration of the tone; response magnitude did increase monotonically with increasing tone level. When a wideband noise was presented alone, nSFOAE magnitude increased over the initial 100-to 200-ms portion of the 400-ms duration of the noise. When the tone and the wideband noise were presented simultaneously, nSFOAE magnitude decreased momentarily, then increased substantially for about the first 100 ms and then remained strong for the remainder of the presentation. Manipulations of the noise bandwidth revealed that the low-frequency components were primarily responsible for this rising, dynamic response; no rising segment was seen with bandpass or highpass noise. The rising, dynamic nSFOAE response is likely attributable to activation of the medial olivocochlear efferent system. This perstimulatory emission appears to have the potential to provide information about the earliest stages of auditory processing for stimuli commonly used in psychoacoustical tasks.

The time course of cochlear gain reduction measured using a more efficient psychophysical technique

“…5. The onset delays are roughly similar to those reported by Backus and Guinan ͑2006͒, and the buildup time constants are consistent with those reported by Walsh et al ͑2010b͒ with the short analysis window.…”

“…The onset and offset delays are in the range reported by Backus and Guinan ͑2006͒, although the buildup and decay time constants in the present study were shorter. Buildup time constants we report are similar to those reported by Walsh et al ͑2010b͒ for nSFOAEs using their short analysis window.…”

“…9͑b͒. Subjects who did show buildup within precursor duration for short delays ͑S2, S3 and S5͒ had buildup time constants similar to those reported by Walsh et al ͑2010b͒ for nSFOAEs when a 20-ms analysis window was used. This suggests that the minimum-delay points for these subjects are positioned as shown in Fig.…”

“…8͒ shows that maximum TE grows with precursor duration. Walsh et al ͑2010b͒ ͑Fig. 9͒ reported a similar effect of elicitor duration in their nSFOAE study.…”

“…The TE seems to plateau after roughly 200 ms or so ͑Zwicker, 1965; Bacon and Moore, 1986͒. Assuming the masker onset elicits the MOCR, any TE in the first 25 ms from the onset of the masker should not be due to gain reduction by the MOCR, because of the onset delay documented by Backus andWalsh et al ͑2010b͒. Given the time steps that have been used, as well as variability in the data, it is often not possible to determine precisely how much of a change in threshold there is within the first 25 ms.…”