Exploring Optimal Stimulus Frequency Ratio for Measurement of the Quadratic f2–f1 Distortion Product Otoacoustic Emission in Humans Purpose Distortion product otoacoustic emissions (DPOAEs) are a by-product of active cochlear processes that lead to the compressive nonlinearity of healthy ears. The most commonly studied emission is at the frequency 2f1–f2, but there has been recent interest in using the quadratic distortion product at the frequency f2–f1 to detect ... Research Article
Research Article  |   July 13, 2018
Exploring Optimal Stimulus Frequency Ratio for Measurement of the Quadratic f2–f1 Distortion Product Otoacoustic Emission in Humans
 
Author Affiliations & Notes
  • Rachael R. Baiduc
    Department of Speech, Language, and Hearing Sciences, University of Colorado–Boulder
  • Sumitrajit Dhar
    Roxelyn and Richard Pepper Department of Communication Sciences and Disorders, Northwestern University, Evanston, IL
    Knowles Hearing Center, Northwestern University, Evanston, IL
  • Disclosure: The authors have declared that no competing interests existed at the time of publication.
    Disclosure: The authors have declared that no competing interests existed at the time of publication. ×
  • Correspondence to Rachael R. Baiduc: Rachael.Baiduc@colorado.edu
  • Editor-in-Chief: Frederick (Erick) Gallun
    Editor-in-Chief: Frederick (Erick) Gallun×
  • Editor: Steve Aiken
    Editor: Steve Aiken×
Article Information
Hearing Disorders / Hearing / Research Articles
Research Article   |   July 13, 2018
Exploring Optimal Stimulus Frequency Ratio for Measurement of the Quadratic f2–f1 Distortion Product Otoacoustic Emission in Humans
Journal of Speech, Language, and Hearing Research, July 2018, Vol. 61, 1794-1806. doi:10.1044/2018_JSLHR-H-17-0349
History: Received September 15, 2017 , Revised January 21, 2018 , Accepted March 2, 2018
 
Journal of Speech, Language, and Hearing Research, July 2018, Vol. 61, 1794-1806. doi:10.1044/2018_JSLHR-H-17-0349
History: Received September 15, 2017; Revised January 21, 2018; Accepted March 2, 2018

Purpose Distortion product otoacoustic emissions (DPOAEs) are a by-product of active cochlear processes that lead to the compressive nonlinearity of healthy ears. The most commonly studied emission is at the frequency 2f1–f2, but there has been recent interest in using the quadratic distortion product at the frequency f2–f1 to detect cochleopathies including endolymphatic hydrops. Before the DPOAE at f2–f1 can be applied clinically in any capacity, optimal stimulus parameters for its elicitation must be established.

Method We investigated stimulus parameters for the DPOAEs at f2–f1 and 2f1–f2 in 23 adults with normal hearing. Logarithmically swept tones between approximately 0.6 and 20 kHz (L1 = L2 = 70 dB SPL) served as the higher frequency stimulus (f2). DPOAEs were measured for 6 f2/f1 ratios: 1.14, 1.18, 1.22, 1.30, 1.32, and 1.36.

Results Both DPOAEs were consistently measurable. In line with previous investigations, the highest levels of the DPOAE at 2f1–f2 were generated between f2/f1 ratios of 1.14–1.22, with a peak in the level ratio function at 1.22. In contrast, f2–f1 was less influenced by ratio, although the narrowest ratio (1.14) produced slightly higher levels across frequency.

Conclusion The DPOAE at f2–f1 is measurable in individuals with normal hearing up to f2 of 20 kHz at narrow f2/f1 ratios. Measurements at additional stimulus levels and in subjects with hearing impairment will be needed before clinical implementation.

Acknowledgments
This work was supported by a grant to Sumitrajit Dhar from the Knowles Hearing Center at Northwestern University. The authors wish to thank Dr. Diana Callesano and Ms. Emily Kahn for assistance with data collection. Additional thanks are due to Drs. Mary Ann Cheatham, Jason Sanchez, and Jonathan Siegel for their ongoing input regarding data interpretation and manuscript preparation. They also wish to thank the subjects for the time and dedication they committed to participating in these experiments.
Portions of this work were presented in “Exploring Stimulus Conditions for Measurement of the Quadratic f2–f1 Distortion Product Otoacoustic Emission,” Proceedings of Association for Research in Otolaryngology Conference, Baltimore, MD, February 2013.
This work was completed as part of Dr. Baiduc's dissertation at Department of Communication Sciences and Disorders, Northwestern University, Evanston, IL 60208.
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