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. Over the next five years we propose innovative modeling and measurements to address important issues of cochlear function while improving our understanding of OAE generation.
Aim 1 explores cochlear nonlinearities using OAEs.
Aim 1 a studies the form of cochlear gain control using OAE measurements and models to probe the dynamics of compression and suppression using paired clicks.
Aim 1 b studies the action of suppressor tones on OAE generation by testing their ability to map out the distribution of OAE generators in models where the distribution is known.
Aim 2 studies how OAEs depend on mechanisms of cochlear amplification.
Aim 2 a explores OAE generation in response-matched cochlear models that employ push-pull amplification to test arguments that push- pull models cannot produce realistic OAEs.
Aim 2 b studies spontaneous OAEs (SOAEs) in models of the lizard cochlea-a species where the biophysics of amplification is fundamentally different from the mammal-to test the hypothesis that lizard SOAEs nevertheless arise through mechanisms analogous to those in mammals.
Aim 3 probes cochlear apical/basal differences using OAEs.
Aim 3 a pursues the emerging idea that the base and apex are very different by building on our discovery of an otoacoustic/mechanical transition near the midpoint of the cochlea. Models derived from data will test the hypothesis that the OAE transition results from wave reflection at the mechanical seam.
Aim 3 b uses measurements and models to characterize apical mechanics and the OAE transition, testing hypotheses that relate the transition to the breaking of scaling symmetry. Completion of these Aims will significantly enhance our understanding of OAE generation and its relationship to cochlear mechanics across species and along the cochlea.
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.

Public Health Relevance

Our experiments and models address the mechanisms by which healthy ears generate sound. Sounds from the ear, known as otoacoustic emissions (OAEs), are widely used for noninvasive tests of hearing function. By improving our understanding of how OAEs are produced within the cochlea, and how they can be used to probe aspects of cochlear function important for human communication, the proposed work will enhance the power of clinical hearing tests and help improve the design of auditory prosthetic devices.

National Institute of Health (NIH)
National Institute on Deafness and Other Communication Disorders (NIDCD)
Research Project (R01)
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Auditory System Study Section (AUD)
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Miller, Roger
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Massachusetts Eye and Ear Infirmary
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Christensen, Anders T; Abdala, Carolina; Shera, Christopher A (2018) Probing Apical-Basal Differences in the Human Cochlea Using Distortion-Product Otoacoustic Emission Phase. AIP Conf Proc 1965:
Sisto, Renata; Shera, Christopher A; Moleti, Arturo (2018) Negative-delay sources in distortion product otoacoustic emissions. Hear Res 360:25-30
Charaziak, Karolina K; Dong, Wei; Shera, Christopher A (2018) Temporal Suppression of Clicked-Evoked Otoacoustic Emissions and Basilar-Membrane Motion in Gerbils. AIP Conf Proc 1965:
Shera, Christopher A; Charaziak, Karolina K (2018) Cochlear Frequency Tuning and Otoacoustic Emissions. Cold Spring Harb Perspect Med :
Sumner, Christian J; Wells, Toby T; Bergevin, Christopher et al. (2018) Mammalian behavior and physiology converge to confirm sharper cochlear tuning in humans. Proc Natl Acad Sci U S A 115:11322-11326
Gruters, Kurtis G; Murphy, David L K; Jenson, Cole D et al. (2018) The eardrums move when the eyes move: A multisensory effect on the mechanics of hearing. Proc Natl Acad Sci U S A 115:E1309-E1318
Abdala, Carolina; Guardia, Yeini C; Shera, Christopher A (2018) Swept-tone stimulus-frequency otoacoustic emissions: Normative data and methodological considerations. J Acoust Soc Am 143:181
Moleti, Arturo; Sisto, Renata; Shera, Christopher A (2018) Introducing Causality Violation for Improved DPOAE Component Unmixing. AIP Conf Proc 1965:
Charaziak, Karolina K; Siegel, Jonathan H; Shera, Christopher A (2018) Spectral Ripples in Round-Window Cochlear Microphonics: Evidence for Multiple Generation Mechanisms. J Assoc Res Otolaryngol 19:401-419
Abdala, Carolina; Ortmann, Amanda J; Shera, Christopher A (2018) Reflection- and Distortion-Source Otoacoustic Emissions: Evidence for Increased Irregularity in the Human Cochlea During Aging. J Assoc Res Otolaryngol 19:493-510

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