Distortion product otoacoustic mapping measured pre- and post-loud sound exposures

Abstract

Objective

Sampling distortion product otoacoustic emissions (DPOAEs) at multiple f₂/f₁ ratios and f₂ frequency values produces a DPOAE “map.” This study examined the efficacy of DPOAE mapping compared with pure tone audiometry and standard DPOAEs for detecting noise effects in subjects exposed to loud sound.

Design

A map significance score was developed as a single measure of map change. Significance scores were evaluated before and after exposure to: loud music (LM), controlled noise (CN), and firing range noise (FR) in three separate sets of subjects. Scores were compared to audiometry and standard DPOAE results in the LM study.

Study sample

The LM and CN exposure studies involved 22, and 20 healthy young subjects respectively with normal hearing. Eight Marines were studied before and after FR exposure.

Results

After LM exposure, audiometry showed significant changes at 1, 2, 4, and 6 kHz. Standard DPOAE measures were also significantly different at several frequencies. Map significance scores detected changes more effectively and showed the distribution of DPOAE alterations.

Conclusions

Map significance scores detected changes after noise exposure more reliably than audiometry and standard DPOAEs. Additionally, maps showed a diffuse response to sound exposure perhaps explaining why individual DP-grams appear less sensitive.

Keywords:

• Outer hair cells: noise-induced hearing loss: hearing tests: distortion product otoacoustic emissions

Acknowledgements

We thank Dr. Brenda Lonsbury-Martin and Dr. Glen Martin for their help with the testing and developing of the DPOAE mapping hardware and protocols. We appreciate the assistance and sage advice from Dawn Konrad-Martin, Ph.D. and Deanna Meinke, Ph.D. We thank Bradley Q. Fox and Torri Lee for their assistance with the testing at Dartmouth. We would like to thank all the individuals who participated in the study.

Disclosure statement

The views expressed in this manuscript are those of the authors and do not necessarily reflect the official policy or position of the Department of the Navy, Department of Defense, nor the U.S. Government. Neither the Department of the Navy nor any other component of the Department of Defense has approved, endorsed, or authorised this manuscript. CDR Sean R. Wise was a military service member. This work was prepared as part of his official duties. Title 17, U.S.C. §105 provides that copyright protection under this title is not available for any work of the U.S. Government. Title 17, U.S.C., §101 defines a U.S. Government work as a work prepared by a military service member or employee of the U.S. Government as part of that person’s official duties.

Data availability statement

The data that support the findings of this study are available on request from the corresponding author, JCB. The data are not publicly available due to their containing information that could compromise the privacy of research participants and to the fact that data were collected at different institutions with different data sharing requirements.

Additional information

Funding

This work is supported by Office of Naval Research Grant No. N00014-16-1-2330.