^{1,a)}, Stephen T. Neely

^{1}, Darcia M. Dierking

^{1}, Judy Kopun

^{1}, Kristin Jolkowski

^{1}, Kristin Groenenboom

^{1}, Hongyang Tan

^{1}and Bettina Stiegemann

^{1}

### Abstract

Distortion product otoacoustic emission suppression (quantified as decrements) was measured for and , for a range of primary levels , suppressor frequencies , and suppressor levels in 19 normal-hearing subjects. Slopes of decrement-versus- functions were similar at both frequencies, and decreased as increased. Suppression tuning curves, constructed from decrement functions, were used to estimate (1) suppression for on- and low-frequency suppressors, (2) tip-to-tail differences, (3) , and (4) best frequency. Compression, estimated from the slope of functions relating suppression “threshold” to for off-frequency suppressors, was similar for 500 and . Tip-to-tail differences, , and best frequency decreased as increased for both frequencies. However, tip-to-tail difference (an estimate of cochlear-amplifier gain) was greater at , compared to . decreased to a greater extent with when , but, on an octave scale, best frequency shifted more with level when . These data indicate that, at both frequencies, cochlear processing is nonlinear. Response growth and compression are similar at the two frequencies, but gain is greater at and spread of excitation is greater at .

This work was supported by the NIH (NIDCD R01 DC002251 and P30 DC004662). We thank Sandy Estee for her assistance in subject recruitment, Sarah Michaels for help constructing some of the figures, and the subjects who made the time commitment that was necessary to complete their participation in the study. We also would like to thank Chris Shera and Andy Oxenham for constructive discussions of these data prior to submission, and two anonymous reviewers who provided helpful suggestions on a previous version of the manuscript.

I. INTRODUCTION

II. METHODS

A. Subjects

B. Stimuli

C. Procedures

III. RESULTS

A. Control conditions

B. Decrement-versus-suppressor level functions

C. Suppression tuning curves

D. Quantitative descriptions of the DPOAE STCs

IV. DISCUSSION

### Key Topics

- Sound pressure
- 20.0
- Frequency measurement
- 7.0
- Otoacoustic emission
- 6.0
- Audiometry
- 5.0
- Calibration
- 4.0

## Figures

Top row: Mean DPOAE (squares) and noise (triangles) levels in dB SPL as a function of suppressor level, , in dB SPL. Bottom row: Mean DPOAE decrements (circles) in dB as a function of . Left column shows data when ; right column shows data when . In both cases, SL, and an on-frequency suppressor was used ( and for and , respectively). Closed symbols represent the transformed data points and the line represents a linear regression fit to the closed symbols. In all cases, error bars represent The short vertical dashed lines in the bottom row of panels are drawn at a decrement of , which was used as suppression threshold for the construction of STCs.

Top row: Mean DPOAE (squares) and noise (triangles) levels in dB SPL as a function of suppressor level, , in dB SPL. Bottom row: Mean DPOAE decrements (circles) in dB as a function of . Left column shows data when ; right column shows data when . In both cases, SL, and an on-frequency suppressor was used ( and for and , respectively). Closed symbols represent the transformed data points and the line represents a linear regression fit to the closed symbols. In all cases, error bars represent The short vertical dashed lines in the bottom row of panels are drawn at a decrement of , which was used as suppression threshold for the construction of STCs.

DPOAE and noise levels for the control conditions, in which there was no suppressor. Top: Mean DPOAE (squares) and noise (triangles) levels in dB SPL as a function of in dB SL when . Bottom: Mean DPOAE (squares) and noise (triangles) levels in dB SPL as a function of in dB SL when . In both panels, error bars represent

DPOAE and noise levels for the control conditions, in which there was no suppressor. Top: Mean DPOAE (squares) and noise (triangles) levels in dB SPL as a function of in dB SL when . Bottom: Mean DPOAE (squares) and noise (triangles) levels in dB SPL as a function of in dB SL when . In both panels, error bars represent

Mean DPOAE decrements in dB as a function of in dB SPL when and SL. Error bars represent Suppressor frequency is indicated within each panel. Closed symbols represent the transformed data to which a linear regression, represented by the solid line, was fit. The short vertical dashed lines in each panel are drawn at a decrement of , which was used as suppression threshold for the construction of STCs.

Mean DPOAE decrements in dB as a function of in dB SPL when and SL. Error bars represent Suppressor frequency is indicated within each panel. Closed symbols represent the transformed data to which a linear regression, represented by the solid line, was fit. The short vertical dashed lines in each panel are drawn at a decrement of , which was used as suppression threshold for the construction of STCs.

Mean DPOAE decrements in dB as a function of in dB SPL when and SL. Error bars represent Suppressor frequency is indicated within each panel. Closed symbols represent the transformed data to which a linear regression, represented by the solid line, was fit. The short vertical dashed lines in each panel are drawn at a decrement of , which was used as suppression threshold for the construction of STCs.

Mean slopes of the decrement-vs- functions as a function of for (circles) and (triangles). Data are plotted on a log frequency scale in the left column and a relative (octave) frequency scale in the right column.

Mean slopes of the decrement-vs- functions as a function of for (circles) and (triangles). Data are plotted on a log frequency scale in the left column and a relative (octave) frequency scale in the right column.

Mean suppression tuning curves, in which the for of suppression is plotted as a function of , following the conventions used in Fig. 5.

Mean suppression tuning curves, in which the for of suppression is plotted as a function of , following the conventions used in Fig. 5.

Slopes of the decrement functions as a function of , based on multiple linear regression in which and were included in the regression analysis. Open symbols represent the slopes of the decrement-vs- functions and closed symbols represent the slope of the decrements vs . Circles represent data when and triangles represent data when .

Slopes of the decrement functions as a function of , based on multiple linear regression in which and were included in the regression analysis. Open symbols represent the slopes of the decrement-vs- functions and closed symbols represent the slope of the decrements vs . Circles represent data when and triangles represent data when .

Mean STCs for 500 and . Top: STCs constructed using simple linear regressions that were fit to the decrement-vs- functions. Bottom: STCs constructed using multiple linear regressions that were fit to the decrement-vs- functions. Within each panel, increases from the STC with the lowest suppression threshold to the highest. Superimposed in both panels are the mean behavioral thresholds (closed circles) for all the and frequencies used in the present study.

Mean STCs for 500 and . Top: STCs constructed using simple linear regressions that were fit to the decrement-vs- functions. Bottom: STCs constructed using multiple linear regressions that were fit to the decrement-vs- functions. Within each panel, increases from the STC with the lowest suppression threshold to the highest. Superimposed in both panels are the mean behavioral thresholds (closed circles) for all the and frequencies used in the present study.

for of suppression as a function of (dB SL) for on-frequency (closed squares) and low-frequency (open squares) suppressors. The low-frequency suppressor was approximately 1 octave below . Top and bottom rows show results for simple and multiple linear regressions, respectively. Left and right columns show data for and , respectively. The lines represent linear fits to each set of data. Slopes of these lines are provided as insets adjacent to the line to which they apply.

for of suppression as a function of (dB SL) for on-frequency (closed squares) and low-frequency (open squares) suppressors. The low-frequency suppressor was approximately 1 octave below . Top and bottom rows show results for simple and multiple linear regressions, respectively. Left and right columns show data for and , respectively. The lines represent linear fits to each set of data. Slopes of these lines are provided as insets adjacent to the line to which they apply.

Tip-to-tail difference (in dB) as a function of (dB SL) when (open circles) and when (closed circles). Top and bottom panels show the results for simple and multiple linear regressions, respectively.

Tip-to-tail difference (in dB) as a function of (dB SL) when (open circles) and when (closed circles). Top and bottom panels show the results for simple and multiple linear regressions, respectively.

as a function of (dB SL) following the conventions used in Fig. 10.

as a function of (dB SL) following the conventions used in Fig. 10.

Best frequency in octaves (re: ) as a function of (dB SL), following the conventions used in Figs. 10 and 11. The dashed line is drawn at 0 octaves relative to and provides a point of reference.

Best frequency in octaves (re: ) as a function of (dB SL), following the conventions used in Figs. 10 and 11. The dashed line is drawn at 0 octaves relative to and provides a point of reference.

Tip-to-tail difference as a function of , following the convention used in Figs. 10–12. Circles represents data for and triangles represent data for . For both frequencies, the point with the lowest tip-to-tail difference/ represents results for the highest level ( SL at both frequencies) and the points with the largest /tip-to-tail difference represent results for the lowest levels ( SL at and SL at ). Lines in each panel (SLR and MLR) represent linear fits to the data.

Tip-to-tail difference as a function of , following the convention used in Figs. 10–12. Circles represents data for and triangles represent data for . For both frequencies, the point with the lowest tip-to-tail difference/ represents results for the highest level ( SL at both frequencies) and the points with the largest /tip-to-tail difference represent results for the lowest levels ( SL at and SL at ). Lines in each panel (SLR and MLR) represent linear fits to the data.

## Tables

Means and standard deviations for the control condition in each of the 19 subjects at each of the four levels when . Grand means and standard deviations are provided in the bottom two rows.

Means and standard deviations for the control condition in each of the 19 subjects at each of the four levels when . Grand means and standard deviations are provided in the bottom two rows.

Means and standard deviations for the control condition in each of the 19 subjects at each of the five levels when . Grand means and standard deviations are provided in the bottom two rows.

Means and standard deviations for the control condition in each of the 19 subjects at each of the five levels when . Grand means and standard deviations are provided in the bottom two rows.

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