# Understanding Otoacoustic Emissions

> **NIH NIH R01** · UNIVERSITY OF SOUTHERN CALIFORNIA · 2020 · $471,243

## Abstract

Project Summary
Realizing the potential of otoacoustic emissions (OAEs) as noninvasive probes of cochlear function
requires understanding the physical and physiological mechanisms that generate and shape these
sounds. To address important unresolved issues of cochlear mechanics while improving our
understanding of OAE generation, we propose three aims involving innovative theoretical modeling
rigorously tested by experimental measurements. The first Aim studies the action of “suppressor”
tones on OAE generation by testing the hypothesis that suppressors can both reduce the strength of
existing OAE sources and create new sources of wave reflection within the cochlea. We determine
whether suppressors can accurately map out the distribution of OAE generators in models where the
distribution is known in advance and test whether eliminating sources created by the suppressor can
improve the measurement of cochlear frequency selectivity using OAE suppression tuning curves. The
second Aim studies the nature of the micromechanical irregularity believed necessary for the
generation of reflection-source OAEs. We test whether efferent-induced changes in OAEs can be
explained by the hypothesis that activation of medial olivocochlear (MOC) efferents alters the spatial
pattern of irregularity. Using both measurements and models, we also explore the hypothesized but
previously unrecognized role of irregularity on the generation of distortion-source OAEs and its
modulation by contralateral acoustic stimulation. The third Aim explores the micromechanics of
cochlear wave amplification and its consequences for OAE generation. Modeling work studies OAE
generation in models incorporating forms of spatial feed-forward/backward amplification suggested by
the oblique geometry of the outer hair cells. We also combine state-of-the-art measurements of organ
of Corti vibration using optical coherence tomography (OCT) with theoretical inverse methods to study
how the assumed coupling between the modes affects the generation and propagation of OAEs.
Completion of these Aims will significantly enhance our understanding of OAE generation and its
relationship to cochlear mechanics. The Aims are also directly relevant to improving the power of
OAE-based diagnostics and other technological applications—such as hearing aids and
preprocessors for speech-recognition devices—that benefit from knowledge of cochlear amplification,
nonlinearity, and signal processing.

## Key facts

- **NIH application ID:** 9899237
- **Project number:** 5R01DC003687-23
- **Recipient organization:** UNIVERSITY OF SOUTHERN CALIFORNIA
- **Principal Investigator:** Christopher A Shera
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $471,243
- **Award type:** 5
- **Project period:** 1999-01-01 → 2024-03-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9899237

## Citation

> US National Institutes of Health, RePORTER application 9899237, Understanding Otoacoustic Emissions (5R01DC003687-23). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/9899237. Licensed CC0.

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