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Christopher A. Shera, PhD

Professor of Otolaryngology-Head and Neck Surgery

Co-Division Chief

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Phone +1 323 865 1685
Email christopher.shera@usc.edu
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Overview

Lab Site:

http://apg.mechanicsofhearing.org

The peripheral auditory system transforms air-borne pressure waves into neural impulses that are interpreted by the brain as sound and speech. The cochlea of the inner ear is a snail-shaped electro-hydromechanical signal amplifier, frequency analyzer, and transducer with an astounding constellation of performance characteristics, including sensitivity to sub-atomic displacements with microsecond mechanical response times; wideband operation spanning three orders-of-magnitude in frequency; an input dynamic range of 120 dB, corresponding to a million-million-fold change in signal energy; useful operation even at signal powers 100 times smaller than the background noise; and ultra-low power consumption (15 µW). All of this is achieved not with the latest silicon technology or by exploiting the power of quantum computers — neither has yet approached the performance of the ear — but by self-maintaining biological tissue, most of which is salty water. How does the ear do it?

The Auditory Physics Group studies how the ear amplifies, analyzes, and creates sound. The goal is not only to understand how the cochlea achieves its astounding sensitivity and dynamic range but to use that knowledge to enhance the power of noninvasive probes of peripheral auditory function (e.g., otoacoustic emissions). Our approach involves a strong, quantitative interplay between theoretical modeling studies and physiological measurements. Ongoing work in the lab focuses on models of cochlear amplification, mechanisms of OAE generation, middle-ear transmission, and comparative studies of cochlear mechanics.

Publications

  • Fluid Focusing Contributes to the BM Vibration Amplification by Boosting the Pressure AIP Conf Proc. 2024 Feb 27; 3062(1). . View in PubMed
  • Does Endolymphatic Hydrops Shift the Cochlear Tonotopic Map? AIP Conf Proc. 2024 Feb 27; 3062(1).. View in PubMed
  • Similar Tuning of Distortion-Product Otoacoustic Emission Ratio Functions and Cochlear Vibrations in Mice AIP Conf Proc. 2024 Feb 27; 3062(1). . View in PubMed
  • The Shape of Noise to Come: Signal vsNoise Amplification in the Active Cochlea. AIP Conf Proc. 2024 Feb 27; 3062(1). . View in PubMed
  • Swept Along: Measuring Otoacoustic Emissions Using Continuously Varying Stimuli J Assoc Res Otolaryngol. 2024 Feb 26. . View in PubMed
  • Noise within: Signal-to-noise enhancement via coherent wave amplification in the mammalian cochlea Phys Rev Res. 2024 Jan-Mar; 6(1). . View in PubMed
  • Individual similarities and differences in eye-movement-related eardrum oscillations (EMREOs) Hear Res. 2023 Dec; 440:108899. . View in PubMed
  • Parametric information about eye movements is sent to the ears Proc Natl Acad Sci U S A. 2023 Nov 28; 120(48):e2303562120. . View in PubMed
  • The Noise Within: Signal-to-Noise Enhancement via Coherent Wave Amplification in the Mammalian Cochlea ArXiv. 2023 Nov 15. . View in PubMed
  • Characterizing a Joint Reflection-Distortion OAE Profile in Humans With Endolymphatic Hydrops Ear Hear. 2023 Nov-Dec 01; 44(6):1437-1450. . View in PubMed
  • Individual similarities and differences in eye-movement-related eardrum oscillations (EMREOs) bioRxiv. 2023 Aug 06. . View in PubMed
  • Conserved features of eye movement related eardrum oscillations (EMREOs) across humans and monkeys bioRxiv. 2023 May 22. . View in PubMed
  • Bandpass Shape of Distortion-Product Otoacoustic Emission Ratio Functions Reflects Cochlear Frequency Tuning in Normal-Hearing Mice J Assoc Res Otolaryngol. 2023 06; 24(3):305-324. . View in PubMed
  • The Long Outer-Hair-Cell RC Time Constant: A Feature, Not a Bug, of the Mammalian Cochlea J Assoc Res Otolaryngol. 2023 04; 24(2):129-145. . View in PubMed
  • The Remarkable Outer Hair Cell: Proceedings of a Symposium in Honour of WE. Brownell. J Assoc Res Otolaryngol. 2023 04; 24(2):117-127. . View in PubMed
  • Crucial 3-D viscous hydrodynamic contributions to the theoretical modeling of the cochlear response J Acoust Soc Am. 2023 01; 153(1):77. . View in PubMed
  • Conserved features of eye movement related eardrum oscillations (EMREOs) across humans and monkeys Philos Trans R Soc Lond B Biol Sci. 2023 09 25; 378(1886):20220340. . View in PubMed
  • Otoacoustic emissions reveal the micromechanical role of organ-of-Corti cytoarchitecture in cochlear amplification Proc Natl Acad Sci U S A. 2023 10 10; 120(41):e2305921120. . View in PubMed
  • Characterizing the Relationship Between Reflection and Distortion Otoacoustic Emissions in Normal-Hearing Adults J Assoc Res Otolaryngol. 2022 Oct; 23(5):647-664. . View in PubMed
  • Overturning the mechanisms of cochlear amplification via area deformations of the organ of Corti J Acoust Soc Am. 2022 10; 152(4):2227. . View in PubMed
  • Auditory filter shapes derived from forward and simultaneous masking at low frequencies: Implications for human cochlear tuning Hear Res. 2022 07; 420:108500. . View in PubMed
  • Whistling While it Works: Spontaneous Otoacoustic Emissions and the Cochlear Amplifier J Assoc Res Otolaryngol. 2022 02; 23(1):17-25. . View in PubMed
  • Interplay between traveling wave propagation and amplification at the apex of the mouse cochlea Biophys J. 2022 08 02; 121(15):2940-2951. . View in PubMed
  • WHAT MAKES HUMAN HEARING SPECIAL? Front Young Minds. 2022; 10.. View in PubMed
  • The Elusive Cochlear Filter: Wave Origin of Cochlear Cross-Frequency Masking J Assoc Res Otolaryngol. 2021 12; 22(6):623-640. . View in PubMed
  • Reflection-Source Emissions Evoked with Clicks and Frequency Sweeps: Comparisons Across Levels J Assoc Res Otolaryngol. 2021 12; 22(6):641-658. . View in PubMed
  • Extended low-frequency phase of the distortion-product otoacoustic emission in human newborns JASA Express Lett. 2021 Jan; 1(1):014404. . View in PubMed
  • Cochlear outer hair cell electromotility enhances organ of Corti motion on a cycle-by-cycle basis at high frequencies in vivo Proc Natl Acad Sci U S A. 2021 10 26; 118(43). . View in PubMed
  • Nonlinear cochlear mechanics without direct vibration-amplification feedback Phys Rev Res. 2020 Feb-Apr; 2(1). . View in PubMed
  • J Acoust Soc Am. 2020 09; 148(3):1585. . View in PubMed
  • Asymmetry and Microstructure of Temporal-Suppression Patterns in Basilar-Membrane Responses to Clicks: Relation to Tonal Suppression and Traveling-Wave Dispersion J Assoc Res Otolaryngol. 2020 04; 21(2):151-170. . View in PubMed
  • The cochlear ear horn: geometric origin of tonotopic variations in auditory signal processing Sci Rep. 2020 11 25; 10(1):20528. . View in PubMed
  • Effects of Forward- and Emitted-Pressure Calibrations on the Variability of Otoacoustic Emission Measurements Across Repeated Probe Fits Ear Hear. 2019 Nov/Dec; 40(6):1345-1358. . View in PubMed
  • Variable-rate frequency sweeps and their application to the measurement of otoacoustic emissions J Acoust Soc Am. 2019 11; 146(5):3457. . View in PubMed
  • Morphological Immaturity of the Neonatal Organ of Corti and Associated Structures in Humans J Assoc Res Otolaryngol. 2019 10; 20(5):461-474. . View in PubMed
  • Constraints imposed by zero-crossing invariance on cochlear models with two mechanical degrees of freedom J Acoust Soc Am. 2019 09; 146(3):1685. . View in PubMed
  • A comparison of ear-canal-reflectance measurement methods in an ear simulator J Acoust Soc Am. 2019 08; 146(2):1350. . View in PubMed
  • On the calculation of reflectance in non-uniform ear canals J Acoust Soc Am. 2019 08; 146(2):1464. . View in PubMed
  • An analytic physically motivated model of the mammalian cochlea J Acoust Soc Am. 2019 01; 145(1):45. . View in PubMed
  • Cochlear Frequency Tuning and Otoacoustic Emissions Cold Spring Harb Perspect Med. 2019 02 01; 9(2). . View in PubMed
  • Introducing Causality Violation for Improved DPOAE Component Unmixing AIP Conf Proc. 2018 May 31; 1965(1). . View in PubMed
  • Probing Apical-Basal Differences in the Human Cochlea Using Distortion-Product Otoacoustic Emission Phase AIP Conf Proc. 2018 May 31; 1965(1). . View in PubMed
  • Reflection- and Distortion-Source Otoacoustic Emissions: Evidence for Increased Irregularity in the Human Cochlea During Aging J Assoc Res Otolaryngol. 2018 10; 19(5):493-510. . View in PubMed
  • Spectral Ripples in Round-Window Cochlear Microphonics: Evidence for Multiple Generation Mechanisms J Assoc Res Otolaryngol. 2018 08; 19(4):401-419. . View in PubMed
  • Negative-delay sources in distortion product otoacoustic emissions Hear Res. 2018 03; 360:25-30. . View in PubMed
  • Swept-tone stimulus-frequency otoacoustic emissions: Normative data and methodological considerations J Acoust Soc Am. 2018 01; 143(1):181. . View in PubMed
  • Mammalian behavior and physiology converge to confirm sharper cochlear tuning in humans Proc Natl Acad Sci U S A. 2018 10 30; 115(44):11322-11326. . View in PubMed
  • The eardrums move when the eyes move: A multisensory effect on the mechanics of hearing Proc Natl Acad Sci U S A. 2018 02 06; 115(6):E1309-E1318. . View in PubMed
  • Temporal Suppression of Clicked-Evoked Otoacoustic Emissions and Basilar-Membrane Motion in Gerbils AIP Conf Proc. 2018; 1965(1). . View in PubMed
  • Dynamics of cochlear nonlinearity: Automatic gain control or instantaneous damping? J Acoust Soc Am. 2017 12; 142(6):3510.. View in PubMed
  • Characterizing spontaneous otoacoustic emissions across the human lifespan J Acoust Soc Am. 2017 03; 141(3):1874. . View in PubMed
  • Compensating for ear-canal acoustics when measuring otoacoustic emissions J Acoust Soc Am. 2017 01; 141(1):515. . View in PubMed
  • Using Cochlear Microphonic Potentials to Localize Peripheral Hearing Loss Front Neurosci. 2017; 11:169. . View in PubMed
  • Frequency shifts in distortion-product otoacoustic emissions evoked by swept tones J Acoust Soc Am. 2016 08; 140(2):936. . View in PubMed
  • Increasing Computational Efficiency of Cochlear Models Using Boundary Layers AIP Conf Proc. 2015 Dec 31; 1703. . View in PubMed
  • Relating the Variability of Tone-Burst Otoacoustic Emission and Auditory Brainstem Response Latencies to the Underlying Cochlear Mechanics AIP Conf Proc. 2015 Dec 31; 1703. . View in PubMed
  • Iterated intracochlear reflection shapes the envelopes of basilar-membrane click responses J Acoust Soc Am. 2015 Dec; 138(6):3717-22. . View in PubMed
  • Optimizing swept-tone protocols for recording distortion-product otoacoustic emissions in adults and newborns J Acoust Soc Am. 2015 Dec; 138(6):3785-99. . View in PubMed
  • Functional modeling of the human auditory brainstem response to broadband stimulation J Acoust Soc Am. 2015 Sep; 138(3):1637-59. . View in PubMed
  • The spiral staircase: tonotopic microstructure and cochlear tuning J Neurosci. 2015 Mar 18; 35(11):4683-90. . View in PubMed
  • On the spatial distribution of the reflection sources of different latency components of otoacoustic emissions J Acoust Soc Am. 2015 Feb; 137(2):768-76. . View in PubMed
  • Increased contralateral suppression of otoacoustic emissions indicates a hyperresponsive medial olivocochlear system in humans with tinnitus and hyperacusis J Neurophysiol. 2014 Dec 15; 112(12):3197-208. . View in PubMed
  • On the method of lumens J Acoust Soc Am. 2014 Dec; 136(6):3126. . View in PubMed
  • Otoacoustic-emission-based medial-olivocochlear reflex assays for humans J Acoust Soc Am. 2014 Nov; 136(5):2697-713. . View in PubMed
  • Macromechanics of Hearing: The Unknown Known AIP Conf Proc. 2014 Jun; 1703. . View in PubMed
  • Distortion-product otoacoustic emission reflection-component delays and cochlear tuning: estimates from across the human lifespan J Acoust Soc Am. 2014 Apr; 135(4):1950-8. . View in PubMed
  • Measuring stimulus-frequency otoacoustic emissions using swept tones J Acoust Soc Am. 2013 Jul; 134(1):356-68. . View in PubMed
  • Basilar-membrane interference patterns from multiple internal reflection of cochlear traveling waves J Acoust Soc Am. 2013 Apr; 133(4):2224-39. . View in PubMed
  • Nonlinear time-domain cochlear model for transient stimulation and human otoacoustic emission J Acoust Soc Am. 2012 Dec; 132(6):3842-8. . View in PubMed
  • Probing cochlear tuning and tonotopy in the tiger using otoacoustic emissions J Comp Physiol A Neuroethol Sens Neural Behav Physiol. 2012 Aug; 198(8):617-24. . View in PubMed
  • Obtaining reliable phase-gradient delays from otoacoustic emission data J Acoust Soc Am. 2012 Aug; 132(2):927-43. . View in PubMed
  • The cochlea as a smart structure Smart Mater Struct. 2012 Jun; 21(6):64001. . View in PubMed
  • Reflectance of acoustic horns and solution of the inverse problem J Acoust Soc Am. 2012 Mar; 131(3):1863-73. . View in PubMed
  • On cochlear impedances and the miscomputation of power gain J Assoc Res Otolaryngol. 2011 Dec; 12(6):671-6. . View in PubMed
  • Can a Static Nonlinearity Account for the Dynamics of Otoacoustic Emission Suppression? AIP Conf Proc. 2011 Nov; 1403(1):257-263.. View in PubMed
  • Tracing Distortion Product (DP) Waves in a Cochlear Model AIP Conf Proc. 2011 Nov; 1403(1):557-562. . View in PubMed
  • Frequency selectivity in Old-World monkeys corroborates sharp cochlear tuning in humans Proc Natl Acad Sci U S A. 2011 Oct 18; 108(42):17516-20. . View in PubMed
  • Distortion products and backward-traveling waves in nonlinear active models of the cochlea J Acoust Soc Am. 2011 May; 129(5):3141-52. . View in PubMed
  • Forward- and Reverse-Traveling Waves in DP Phenomenology: Does Inverted Direction of Wave Propagation Occur in Classical Models? AIP Conf Proc. 2011; 1403.. View in PubMed
  • Otoacoustic Estimates of Cochlear Tuning: Testing Predictions in Macaque AIP Conf Proc. 2011; 1403:286-292. . View in PubMed
  • Auditory sensitivity may require dynamically unstable spike generators: evidence from a model of electrical stimulation J Acoust Soc Am. 2010 Nov; 128(5):EL300-5. . View in PubMed
  • Otoacoustic estimation of cochlear tuning: validation in the chinchilla J Assoc Res Otolaryngol. 2010 Sep; 11(3):343-65. . View in PubMed
  • Posture systematically alters ear-canal reflectance and DPOAE properties Hear Res. 2010 May; 263(1-2):43-51. . View in PubMed
  • Coherent reflection without traveling waves: on the origin of long-latency otoacoustic emissions in lizards J Acoust Soc Am. 2010 Apr; 127(4):2398-409. . View in PubMed
  • Dynamical instability determines the effect of ongoing noise on neural firing J Assoc Res Otolaryngol. 2009 Jun; 10(2):251-67. . View in PubMed
  • Otoacoustic emissions in humans, birds, lizards, and frogs: evidence for multiple generation mechanisms J Comp Physiol A Neuroethol Sens Neural Behav Physiol. 2008 Jul; 194(7):665-83. . View in PubMed
  • Testing coherent reflection in chinchilla: Auditory-nerve responses predict stimulus-frequency emissions J Acoust Soc Am. 2008 Jul; 124(1):381-95. . View in PubMed
  • Comparing stimulus-frequency otoacoustic emissions measured by compression, suppression, and spectral smoothing J Acoust Soc Am. 2007 Dec; 122(6):3562-75. . View in PubMed
  • Cochlear reflectivity in transmission-line models and otoacoustic emission characteristic time delays J Acoust Soc Am. 2007 Dec; 122(6):3554-61. . View in PubMed
  • Laser amplification with a twist: traveling-wave propagation and gain functions from throughout the cochlea J Acoust Soc Am. 2007 Nov; 122(5):2738-58. . View in PubMed
  • Near equivalence of human click-evoked and stimulus-frequency otoacoustic emissions J Acoust Soc Am. 2007 Apr; 121(4):2097-110. . View in PubMed
  • Allen-Fahey and related experiments support the predominance of cochlear slow-wave otoacoustic emissions J Acoust Soc Am. 2007 Mar; 121(3):1564-75. . View in PubMed
  • Cochlear traveling-wave amplification, suppression, and beamforming probed using noninvasive calibration of intracochlear distortion sources J Acoust Soc Am. 2007 Feb; 121(2):1003-16. . View in PubMed
  • Wave propagation patterns in a “classical” three-dimensional model of the cochlea J Acoust Soc Am. 2007 Jan; 121(1):352-62. . View in PubMed
  • Posture-induced changes in distortion-product otoacoustic emissions and the potential for noninvasive monitoring of changes in intracranial pressure Neurocrit Care. 2006; 4(3):251-7. . View in PubMed
  • Coherent reflection in a two-dimensional cochlea: Short-wave versus long-wave scattering in the generation of reflection-source otoacoustic emissions J Acoust Soc Am. 2005 Jul; 118(1):287-313. . View in PubMed
  • J Assoc Res Otolaryngol. 2004 Dec; 5(4):349-59. . View in PubMed
  • Simultaneous measurement of middle-ear input impedance and forward/reverse transmission in cat J Acoust Soc Am. 2004 Oct; 116(4 Pt 1):2187-98. . View in PubMed
  • Mechanisms of mammalian otoacoustic emission and their implications for the clinical utility of otoacoustic emissions Ear Hear. 2004 Apr; 25(2):86-97. . View in PubMed
  • Estimates of human cochlear tuning at low levels using forward and simultaneous masking J Assoc Res Otolaryngol. 2003 Dec; 4(4):541-54. . View in PubMed
  • The origin of SFOAE microstructure in the guinea pig Hear Res. 2003 Sep; 183(1-2):7-17. . View in PubMed
  • Mammalian spontaneous otoacoustic emissions are amplitude-stabilized cochlear standing waves J Acoust Soc Am. 2003 Jul; 114(1):244-62. . View in PubMed
  • Stimulus-frequency-emission group delay: a test of coherent reflection filtering and a window on cochlear tuning J Acoust Soc Am. 2003 May; 113(5):2762-72. . View in PubMed
  • Revised estimates of human cochlear tuning from otoacoustic and behavioral measurements Proc Natl Acad Sci U S A. 2002 Mar 05; 99(5):3318-23. . View in PubMed
  • Small tumor virus genomes are integrated near nuclear matrix attachment regions in transformed cells J Virol. 2001 Dec; 75(24):12339-46. . View in PubMed
  • Intensity-invariance of fine time structure in basilar-membrane click responses: implications for cochlear mechanics J Acoust Soc Am. 2001 Jul; 110(1):332-48. . View in PubMed
  • Frequency glides in click responses of the basilar membrane and auditory nerve: their scaling behavior and origin in traveling-wave dispersion J Acoust Soc Am. 2001 May; 109(5 Pt 1):2023-34. . View in PubMed
  • Distortion-product source unmixing: a test of the two-mechanism model for DPOAE generation J Acoust Soc Am. 2001 Feb; 109(2):622-37. . View in PubMed
  • Interrelations among distortion-product phase-gradient delays: their connection to scaling symmetry and its breaking J Acoust Soc Am. 2000 Dec; 108(6):2933-48. . View in PubMed
  • Middle ear pathology can affect the ear-canal sound pressure generated by audiologic earphones Ear Hear. 2000 Aug; 21(4):265-74. . View in PubMed
  • Acoustic mechanisms that determine the ear-canal sound pressures generated by earphones J Acoust Soc Am. 2000 Mar; 107(3):1548-65. . View in PubMed
  • Evoked otoacoustic emissions arise by two fundamentally different mechanisms: a taxonomy for mammalian OAEs J Acoust Soc Am. 1999 Feb; 105(2 Pt 1):782-98. . View in PubMed
  • The origin of periodicity in the spectrum of evoked otoacoustic emissions J Acoust Soc Am. 1995 Oct; 98(4):2018-47. . View in PubMed
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  • An empirical bound on the compressibility of the cochlea J Acoust Soc Am. 1992 Sep; 92(3):1382-8. . View in PubMed
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  • Phenomenological characterization of eardrum transduction J Acoust Soc Am. 1991 Jul; 90(1):253-62. . View in PubMed
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