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    Christopher A. Shera, PhD

    TitleProfessor of Research Otolaryngology Head & Neck Surgery
    SchoolKeck School of Medicine of USC
    DepartmentOtolaryngology
    Phone+1 323 865 1685
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      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.


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      Publications listed below are automatically derived from MEDLINE/PubMed and other sources, which might result in incorrect or missing publications. Researchers can login to make corrections and additions, or contact us for help.
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      1. Charaziak KK, Shera C, Siegel JH. Using Cochlear Microphonic Potentials to Localize Peripheral Hearing Loss. Front Neurosci. 2017; 11:169. PMID: 28420953.
        View in: PubMed
      2. Charaziak KK, Shera C. Compensating for ear-canal acoustics when measuring otoacoustic emissions. J Acoust Soc Am. 2017 Jan; 141(1):515. PMID: 28147590.
        View in: PubMed
      3. Shera C, Abdala C. Frequency shifts in distortion-product otoacoustic emissions evoked by swept tones. J Acoust Soc Am. 2016 Aug; 140(2):936. PMID: 27586726.
        View in: PubMed
      4. Alkhairy SA, Shera C. Increasing Computational Efficiency of Cochlear Models Using Boundary Layers. AIP Conf Proc. 2015 Dec 31; 1703. PMID: 27175041.
        View in: PubMed
      5. Verhulst S, Shera C. 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. PMID: 27175040.
        View in: PubMed
      6. Abdala C, Luo P, Shera C. Optimizing swept-tone protocols for recording distortion-product otoacoustic emissions in adults and newborns. J Acoust Soc Am. 2015 Dec; 138(6):3785. PMID: 26723333.
        View in: PubMed
      7. Shera C. Iterated intracochlear reflection shapes the envelopes of basilar-membrane click responses. J Acoust Soc Am. 2015 Dec; 138(6):3717-22. PMID: 26723327.
        View in: PubMed
      8. Verhulst S, Bharadwaj HM, Mehraei G, Shera C, Shinn-Cunningham BG. Functional modeling of the human auditory brainstem response to broadband stimulation. J Acoust Soc Am. 2015 Sep; 138(3):1637-59. PMID: 26428802.
        View in: PubMed
      9. Shera C. The spiral staircase: tonotopic microstructure and cochlear tuning. J Neurosci. 2015 Mar 18; 35(11):4683-90. PMID: 25788685.
        View in: PubMed
      10. Sisto R, Moleti A, Shera C. 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. PMID: 25698011.
        View in: PubMed
      11. Shera C. On the method of lumens. J Acoust Soc Am. 2014 Dec; 136(6):3126. PMID: 25480060.
        View in: PubMed
      12. Marshall L, Lapsley Miller JA, Guinan JJ, Shera C, Reed CM, Perez ZD, Delhorne LA, Boege P. Otoacoustic-emission-based medial-olivocochlear reflex assays for humans. J Acoust Soc Am. 2014 Nov; 136(5):2697-713. PMID: 25373970.
        View in: PubMed
      13. Knudson IM, Shera C, Melcher JR. 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. PMID: 25231612.
        View in: PubMed
      14. Shera C. Macromechanics of Hearing: The Unknown Known. AIP Conf Proc. 2014 Jun; 1703. PMID: 27630377.
        View in: PubMed
      15. Abdala C, Guérit F, Luo P, Shera C. 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. PMID: 25234993.
        View in: PubMed
      16. Kalluri R, Shera C. Measuring stimulus-frequency otoacoustic emissions using swept tones. J Acoust Soc Am. 2013 Jul; 134(1):356-68. PMID: 23862813.
        View in: PubMed
      17. Shera C, Cooper NP. Basilar-membrane interference patterns from multiple internal reflection of cochlear traveling waves. J Acoust Soc Am. 2013 Apr; 133(4):2224-39. PMID: 23556591.
        View in: PubMed
      18. Verhulst S, Dau T, Shera C. Nonlinear time-domain cochlear model for transient stimulation and human otoacoustic emission. J Acoust Soc Am. 2012 Dec; 132(6):3842-8. PMID: 23231114.
        View in: PubMed
      19. Shera C, Bergevin C. Obtaining reliable phase-gradient delays from otoacoustic emission data. J Acoust Soc Am. 2012 Aug; 132(2):927-43. PMID: 22894215.
        View in: PubMed
      20. Elliott SJ, Shera C. The cochlea as a smart structure. Smart Mater Struct. 2012 Jun; 21(6):64001. PMID: 23148128.
        View in: PubMed
      21. Bergevin C, Walsh EJ, McGee J, Shera C. 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. PMID: 22645048.
        View in: PubMed
      22. Rasetshwane DM, Neely ST, Allen JB, Shera C. Reflectance of acoustic horns and solution of the inverse problem. J Acoust Soc Am. 2012 Mar; 131(3):1863-73. PMID: 22423684.
        View in: PubMed
      23. de Boer E, Shera C, Nuttall AL. Tracing Distortion Product (DP) Waves in a Cochlear Model. AIP Conf Proc. 2011 Nov; 1403(1):557-562. PMID: 25284909.
        View in: PubMed
      24. Verhulst S, Shera C, Harte JM, Dau T. Can a Static Nonlinearity Account for the Dynamics of Otoacoustic Emission Suppression? AIP Conf Proc. 2011 Nov; 1403(1):257-263. PMID: 25284908.
        View in: PubMed
      25. Joris PX, Bergevin C, Kalluri R, Mc Laughlin M, Michelet P, van der Heijden M, Shera C. 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. PMID: 21987783.
        View in: PubMed
      26. Shera C, Olson ES, Guinan JJ. On cochlear impedances and the miscomputation of power gain. J Assoc Res Otolaryngol. 2011 Dec; 12(6):671-6. PMID: 21947765.
        View in: PubMed
      27. Sisto R, Moleti A, Botti T, Bertaccini D, Shera C. Distortion products and backward-traveling waves in nonlinear active models of the cochlea. J Acoust Soc Am. 2011 May; 129(5):3141-52. PMID: 21568417.
        View in: PubMed
      28. Shera C, Bergevin C, Kalluri R, Laughlin MM, Michelet P, van der Heijden M, Joris PX. Otoacoustic Estimates of Cochlear Tuning: Testing Predictions in Macaque. AIP Conf Proc. 2011; 1403:286-292. PMID: 24701000.
        View in: PubMed
      29. Sisto R, Shera C, Moleti A, Botti T. Forward- and Reverse-Traveling Waves in DP Phenomenology: Does Inverted Direction of Wave Propagation Occur in Classical Models? AIP Conf Proc. 2011; 1403. PMID: 24376285.
        View in: PubMed
      30. O'Gorman DE, Colburn HS, Shera C. 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. PMID: 21110542.
        View in: PubMed
      31. Shera C, Guinan JJ, Oxenham AJ. Otoacoustic estimation of cochlear tuning: validation in the chinchilla. J Assoc Res Otolaryngol. 2010 Sep; 11(3):343-65. PMID: 20440634.
        View in: PubMed
      32. Bergevin C, Shera C. 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. PMID: 20370023.
        View in: PubMed
      33. Voss SE, Adegoke MF, Horton NJ, Sheth KN, Rosand J, Shera C. Posture systematically alters ear-canal reflectance and DPOAE properties. Hear Res. 2010 May; 263(1-2):43-51. PMID: 20227475.
        View in: PubMed
      34. O'Gorman DE, White JA, Shera C. Dynamical instability determines the effect of ongoing noise on neural firing. J Assoc Res Otolaryngol. 2009 Jun; 10(2):251-67. PMID: 19308644.
        View in: PubMed
      35. Shera C, Tubis A, Talmadge CL. Testing coherent reflection in chinchilla: Auditory-nerve responses predict stimulus-frequency emissions. J Acoust Soc Am. 2008 Jul; 124(1):381-95. PMID: 18646984.
        View in: PubMed
      36. Bergevin C, Freeman DM, Saunders JC, Shera C. 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. PMID: 18500528.
        View in: PubMed
      37. Kalluri R, Shera C. Comparing stimulus-frequency otoacoustic emissions measured by compression, suppression, and spectral smoothing. J Acoust Soc Am. 2007 Dec; 122(6):3562-75. PMID: 18247764.
        View in: PubMed
      38. Sisto R, Moleti A, Shera C. Cochlear reflectivity in transmission-line models and otoacoustic emission characteristic time delays. J Acoust Soc Am. 2007 Dec; 122(6):3554-61. PMID: 18247763.
        View in: PubMed
      39. Shera C. 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. PMID: 18189566.
        View in: PubMed
      40. Kalluri R, Shera C. Near equivalence of human click-evoked and stimulus-frequency otoacoustic emissions. J Acoust Soc Am. 2007 Apr; 121(4):2097-110. PMID: 17471725.
        View in: PubMed
      41. Shera C, Tubis A, Talmadge CL, de Boer E, Fahey PF, Guinan JJ. Allen-Fahey and related experiments support the predominance of cochlear slow-wave otoacoustic emissions. J Acoust Soc Am. 2007 Mar; 121(3):1564-75. PMID: 17407894.
        View in: PubMed
      42. Shera C, Guinan JJ. 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. PMID: 17348523.
        View in: PubMed
      43. de Boer E, Nuttall AL, Shera C. Wave propagation patterns in a "classical" three-dimensional model of the cochlea. J Acoust Soc Am. 2007 Jan; 121(1):352-62. PMID: 17297790.
        View in: PubMed
      44. Voss SE, Horton NJ, Tabucchi TH, Folowosele FO, Shera C. 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. PMID: 16757834.
        View in: PubMed
      45. Shera C, Tubis A, Talmadge CL. 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. PMID: 16119350.
        View in: PubMed
      46. Shera C, Tubis A, Talmadge CL. Do forward- and backward-traveling waves occur within the cochlea? Countering the critique of Nobili et al. J Assoc Res Otolaryngol. 2004 Dec; 5(4):349-59. PMID: 15675000.
        View in: PubMed
      47. Voss SE, Shera C. 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. PMID: 15532651.
        View in: PubMed
      48. Shera C. Mechanisms of mammalian otoacoustic emission and their implications for the clinical utility of otoacoustic emissions. Ear Hear. 2004 Apr; 25(2):86-97. PMID: 15064654.
        View in: PubMed
      49. Goodman SS, Withnell RH, Shera C. The origin of SFOAE microstructure in the guinea pig. Hear Res. 2003 Sep; 183(1-2):7-17. PMID: 13679133.
        View in: PubMed
      50. Oxenham AJ, Shera C. Estimates of human cochlear tuning at low levels using forward and simultaneous masking. J Assoc Res Otolaryngol. 2003 Dec; 4(4):541-54. PMID: 14716510.
        View in: PubMed
      51. Shera C. Mammalian spontaneous otoacoustic emissions are amplitude-stabilized cochlear standing waves. J Acoust Soc Am. 2003 Jul; 114(1):244-62. PMID: 12880039.
        View in: PubMed
      52. Shera C, Guinan JJ. 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. PMID: 12765394.
        View in: PubMed
      53. Shera C, Guinan JJ, Oxenham AJ. Revised estimates of human cochlear tuning from otoacoustic and behavioral measurements. Proc Natl Acad Sci U S A. 2002 Mar 5; 99(5):3318-23. PMID: 11867706.
        View in: PubMed
      54. Shera KA, Shera C, McDougall JK. Small tumor virus genomes are integrated near nuclear matrix attachment regions in transformed cells. J Virol. 2001 Dec; 75(24):12339-46. PMID: 11711624.
        View in: PubMed
      55. Shera C. 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. PMID: 11508959.
        View in: PubMed
      56. Shera C. 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. PMID: 11386555.
        View in: PubMed
      57. Kalluri R, Shera C. Distortion-product source unmixing: a test of the two-mechanism model for DPOAE generation. J Acoust Soc Am. 2001 Feb; 109(2):622-37. PMID: 11248969.
        View in: PubMed
      58. Shera C, Talmadge CL, Tubis A. 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. PMID: 11144585.
        View in: PubMed
      59. Voss SE, Rosowski JJ, Merchant SN, Thornton AR, Shera C, Peake WT. Middle ear pathology can affect the ear-canal sound pressure generated by audiologic earphones. Ear Hear. 2000 Aug; 21(4):265-74. PMID: 10981602.
        View in: PubMed
      60. Voss SE, Rosowski JJ, Shera C, Peake WT. Acoustic mechanisms that determine the ear-canal sound pressures generated by earphones. J Acoust Soc Am. 2000 Mar; 107(3):1548-65. PMID: 10738809.
        View in: PubMed
      61. Shera C, Guinan JJ. 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. PMID: 9972564.
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      62. Zweig G, Shera C. The origin of periodicity in the spectrum of evoked otoacoustic emissions. J Acoust Soc Am. 1995 Oct; 98(4):2018-47. PMID: 7593924.
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      63. Shera C, Zweig G. Noninvasive measurement of the cochlear traveling-wave ratio. J Acoust Soc Am. 1993 Jun; 93(6):3333-52. PMID: 8326061.
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      64. Shera C, Zweig G. An empirical bound on the compressibility of the cochlea. J Acoust Soc Am. 1992 Sep; 92(3):1382-8. PMID: 1401524.
        View in: PubMed
      65. Shera C, Zweig G. Analyzing reverse middle-ear transmission: noninvasive Gedankenexperiments. J Acoust Soc Am. 1992 Sep; 92(3):1371-81. PMID: 1401523.
        View in: PubMed
      66. Shera C, Zweig G. Middle-ear phenomenology: the view from the three windows. J Acoust Soc Am. 1992 Sep; 92(3):1356-70. PMID: 1401522.
        View in: PubMed
      67. Shera C, Zweig G. Phenomenological characterization of eardrum transduction. J Acoust Soc Am. 1991 Jul; 90(1):253-62. PMID: 1880296.
        View in: PubMed
      68. Shera C, Zweig G. Reflection of retrograde waves within the cochlea and at the stapes. J Acoust Soc Am. 1991 Mar; 89(3):1290-305. PMID: 2030216.
        View in: PubMed
      69. Shera C, Zweig G. A symmetry suppresses the cochlear catastrophe. J Acoust Soc Am. 1991 Mar; 89(3):1276-89. PMID: 2030215.
        View in: PubMed
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