Cochlear tuning estimates from level ratio functions of distortion product otoacoustic emissions

Abstract

Objective: Distortion product otoacoustic emission (DPOAE) levels plotted as a function of stimulus frequency ratio demonstrate a bandpass shape. This bandpass shape is narrower at higher frequencies compared to lower frequencies and thus has been thought to be related to cochlear mechanical tuning.

Design: However, the frequency- and level-dependence of these functions above 8 kHz is largely unknown. Furthermore, how tuning estimates from these functions are related to behavioural tuning is not fully understood.

Study Sample: From experiment 1, we report DPOAE level ratio functions (LRF) from seven normal-hearing, young-adults for f₂ = 0.75–16 kHz and two stimulus levels of 62/52 and 52/37 dB FPL. We found that LRFs became narrower as a function of increasing frequency and decreasing level.

Results: Tuning estimates from these functions increased as expected from 1-8 kHz. In experiment 2, we compared tuning estimates from DPOAE LRF to behavioural tuning in 24 normal-hearing, young adults for 1 and 4 kHz and found that behavioural tuning generally predicted DPOAE LRF estimated tuning.

Conclusions: Our findings suggest that DPOAE LRFs generally reflect the tuning profile consistent with basilar membrane, neural, and behavioural tuning. However, further investigations are warranted to fully determine the use of DPOAE LRF as a clinical measure of cochlear tuning.

Keywords:

• Cochlear tuning
• behavioural tuning
• distortion product otoacoustic emissions
• level ratio function

Acknowledgments

Portions of this work were presented at the 44^th Annual Scientific and Technology Conference of the American Auditory Society in Scottsdale, Arizona, the 41st Annual Mid-Winter Meeting of the Association for Research in Otolaryngology in San Diego, California, and the 2018 Hearing Across the Lifespan Conference in Lake Como, Italy.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

Funding for this work was provided by the National Institute on Deafness and Other Communication Disorders Grant F32 DC017352 (awarded to U.S.W.), The Graduate School and Knowles Hearing Center at Northwestern University and the INAIL grant BRiC 2016 ID17/2016.