Applied Physics 483 Optics & Electronics Seminar
Monday, March 30, 2015
4:15 p.m. Spilker 232
“The novel electro-mechanical structure and function of the inner ear”
Charles R. Steele
Professor Emeritus, Mechanical Engineering & Aeronautics and Astronautics
No aspect of the hearing process is free from controversy and/or contradiction. However, there is a consensus on& several basic features. Nerves are restricted in transferring frequency information to the brain. Consequently, mechanical devices are used in the inner ear for useful neural excitation. The semi-circular canals provide low frequency information associated with body motion, while the mammalian cochlea provides high frequency hearing. The cochlea acts as a real-time Fourier analyzer with a mapping of each frequency of the sound to a place along the cochlea. This mapping can be explained by a simplified "box model", containing only water and an elastic partition, whose stiffness is consistent with the geometric and material properties of the basilar membrane in the cochlea. The analysis of the three-dimensional motion remains a challenge for direct numerical methods, but is easily treated by the 'WKB' asymptotic method. This "passive" fluid-elastic response is close to the actual response for high intensity of sound. However, for low intensity in the living mammal, the response is amplified by around two orders of magnitude, due to some "active" process. Recent results seem to confirm that this is due to piezoelectric behavior of the mammalian outer hair cell. (displacement per mV about 10^5 better than PZT!) The organ of Corti contains all the receptor cells and is an integral part of the basilar membrane. Consideration of the geometry of this organ leads to a "feed-forward/negative feed backward" model for the active process. This requires no tuning of the active process, i.e., an "open loop" system with distributed sensors and actuators, which produces sharp tuning in remarkable agreement with the measurements.
Charles R. Steele
1971 - 2003 Professor of Applied Mechanics, Stanford University.
2003- present Professor Emeritus Editor-in-Chief, International Journal of Solids and Structures, 1985 - 2005. (Elsevier).
Editor-in-Chief and Founder, Journal of Mechanics of Materials and Structures, 2005 –2009 (non-Elsevier!).
NIH Claude Pepper Award , 1988.
Humboldt Senior Fellowship Award , 1994.
National Academy of Engineering, 1995
Honorary Ph.D. Zaporozhye State University, Ukraine, 1997.
Eminent Academician of Ukrainian Academy of Higher Education, 1998.
ASME Warner T. Koiter Medal, 1999.
- Wittbrodt, M. J., S. Puria, and C.R. Steele (2006). Developing a physical model of the human cochlea using micro-fabrication methods, Audiology and Neurotology 11:104-112.
- Dumais, J, SL Shaw, CR Steele, SR Long, PM Ray (2006). An anisotropic-viscoplastic model of plant cell morphogenesis by tip growth, International Journal of Developmental Biology 50 (2-3) Sp. Iss. SI: 209-222.
- Jonathan P. Fay, Sunil Puria, and Charles R. Steele (2006). The discordant eardrum. Proceedings of the National Academy of Sciences, 103 (52): 19743-19748.
- Larry E. Miller, Sharon M. Nickols-Richardson, David F. Wootten, Warren K. Ramp, Charles R. Steele, John R. Cotton, James P. Carneal, and William G. Herbert (2009). Isokinetic Resistance Training Increases Tibial Bending Stiffness in Young Women, Calcified Tissue International 84(6) 446-452.
- Yong-Jin Yoon, Sunil Puria, and Charles R. Steele (2011). Interspecies comparison with three-dimensional cochlear model: Gerbil, Chinchilla, Cat, and Human, Biophysical Journal 100(1) 1-10.
- Soons, Joris A.M., Anthony J. Ricci, Charles R. Steele, Sunil Puria (2014). Cytoarchitecture of the mouse organ of Corti from base to apex, determined using in-situ two-photon imaging. Journal of the Association for Research in Otolaryngology (DOI 10.1007/s10162-014-0497-1).