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.
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.
|Knudson, Inge M; Shera, Christopher A; Melcher, Jennifer R (2014) Increased contralateral suppression of otoacoustic emissions indicates a hyperresponsive medial olivocochlear system in humans with tinnitus and hyperacusis. J Neurophysiol 112:3197-208|
|Abdala, Carolina; Guérit, François; Luo, Ping et al. (2014) Distortion-product otoacoustic emission reflection-component delays and cochlear tuning: estimates from across the human lifespan. J Acoust Soc Am 135:1950-8|
|Lichtenhan, Jeffery T; Cooper, Nigel P; Guinan Jr, John J (2013) A new auditory threshold estimation technique for low frequencies: proof of concept. Ear Hear 34:42-51|
|Kalluri, Radha; Shera, Christopher A (2013) Measuring stimulus-frequency otoacoustic emissions using swept tones. J Acoust Soc Am 134:356-68|
|Shera, Christopher A; Cooper, Nigel P (2013) Basilar-membrane interference patterns from multiple internal reflection of cochlear traveling waves. J Acoust Soc Am 133:2224-39|
|Rasetshwane, Daniel M; Neely, Stephen T; Allen, Jont B et al. (2012) Reflectance of acoustic horns and solution of the inverse problem. J Acoust Soc Am 131:1863-73|
|Lichtenhan, Jeffery T (2012) Effects of low-frequency biasing on otoacoustic and neural measures suggest that stimulus-frequency otoacoustic emissions originate near the peak region of the traveling wave. J Assoc Res Otolaryngol 13:17-28|
|Shera, Christopher A; Olson, Elizabeth S; Guinan Jr, John J (2011) On cochlear impedances and the miscomputation of power gain. J Assoc Res Otolaryngol 12:671-6|
|Sisto, Renata; Moleti, Arturo; Botti, Teresa et al. (2011) Distortion products and backward-traveling waves in nonlinear active models of the cochlea. J Acoust Soc Am 129:3141-52|
|Joris, Philip X; Bergevin, Christopher; Kalluri, Radha et al. (2011) Frequency selectivity in Old-World monkeys corroborates sharp cochlear tuning in humans. Proc Natl Acad Sci U S A 108:17516-20|
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