05 Mar

Speaker: Dr. Karim Sabra

Join us next Tuesday for our 2nd ASA spring 2013 lecture! The speaker will be ME professor Dr. Karim Sabra. Below is a brief description of the lecture topic and his past experience in acoustics.

Update 3/11/2013: There has been a change in the lecture topic. Please see below for information about the new topic.

High-frequency SONAR imaging fundamentals

SONAR is an acronym for SOund Navigation And Ranging. The basic principle of sonar is to use sound to detect or locate objects, typically in the ocean. Sonar technology is similar to other technologies such as: RADAR (RAdio Detection And Ranging); ultrasound, which typically uses higher frequencies for medical applications; and seismic processing, which typically uses lower frequencies in sediments. The principle of Synthetic aperture sonar (SAS) is to combine successive pings coherently along a known track in order to increase the azimuth (along-track) resolution. SAS has the potential to produce high resolution images down to centimeter resolution up to hundreds of meters range. I will present the physical principles and signal processing underlaying SAS. Several examples will be introduced to show that SAS a suitable technique for imaging of the seafloor for applications such as search for small objects, imaging of wrecks, underwater archaeology and pipeline inspection

Date: Tuesday, March 12th, 2013
Time: 11:00 am
Location: Love Bldg. Rm 109

Karim Sabra is currently an Associate Professor of Mechanical Engineering at the Georgia Institute of Technology. Prof. Sabra joined the Georgia Institute of Technology in July 2007. Prior to this he was a Project Scientist (for 2 years) and Postdoctoral researcher (for 2 years) at the Marine Physical Laboratory of the Scripps Institute of Oceanography at the University of California at San Diego. Prof. Sabra graduated with his PhD in Mechanical Engineering in 2003 from the University of Michigan at Ann Arbor, completing his PhD studies in 3 years. Prof. Sabra teaches and performs research on acoustic and elastic wave propagation. Dr. Sabra’s awards include election as a Fellow of the Acoustical Society of America in 2007, the 2009 A.B. Wood medal from the Institute of Acoustics (UK) for his significant contributions to the field of underwater acoustics and the 2011 R.B. Lindsay award from the Acoustical Society of America for significant contribution to time-reversal and ambient noise correlations.

01 Mar

Dr. Julien Meaud Faculty Candidate Seminar

There will be an upcoming faculty candidate seminar given by Dr. Julien Meaud on the non-linear dynamics of the cochlea. See below for more information about this interesting topic!

Simulating the active nonlinear dynamics of the cochlea using a computational multi-physics model

The mammalian ear is able to sense faint sounds (down to 0 dB SPL), distinguish between close frequencies (0.1% apart) and operate over a broad range of sound intensities (6 orders of magnitude). This striking performance is due to the presence of an active feedback mechanism linked to outer hair cell activity in the sensory organ of the inner ear, the cochlea. Thanks to this feedback mechanism, called cochlear amplifier, the cochlea is a nonlinear system that exhibits high sensitivity and sharp tuning in response to low level sounds and a broad dynamic range. Failure of the cochlear amplifier due to diseases, ototoxic drugs, sound overexposure or aging causes deafness or hearing loss. Better understanding of how the cochlea processes sounds is needed to better protect hearing, diagnose hearing pathologies and treat hearing loss. Development of computational models of the cochlea allows testing theories of active cochlear mechanics and could have both scientific and clinical applications. In this talk I will present a nonlinear multi-physics model of the cochlea. This computational model, formulated in the frequency domain using an alternating frequency/time method, couples the mechanical, electrical and acoustical domains of the cochlea using finite element methods and includes detailed models for the biophysics of outer hair cells. I will demonstrate that this physically-motivated model is able to simulate the main aspects of the nonlinear response of the cochlea to single-tone and two-tone stimuli. Finally, I will show that the model can be used as a virtual laboratory that can test for example the effect of genetic mutations on cochlear tuning.

Date: Wednesday, March 27th, 2013
Time: 11:00 am
Location: MRDC Rm 4211

Julien Meaud is currently a Research Fellow in the Vibrations and Acoustics Laboratory in the Department of Mechanical Engineering at the University of Michigan, Ann Arbor, where he works on computational cochlear mechanics under the supervision of Prof. Karl Grosh. He studied engineering as an undergraduate at the Ecole Centrale de Lyon in France. He received a Master of Science in 2006 and a Ph. D. in Mechanical Engineering in 2010, both from the University of Michigan. His work on cochlear mechanics has been published in the major journals of acoustical and biophysical research. He was awarded a best student paper award at the 2009 Acoustical Society Meeting for a presentation of his computational model of the cochlea. Prior to his current postdoctoral appointment, he worked with Prof. Gregory Hulbert as a Research Fellow in the Computational Mechanics Laboratory at the University of Michigan and investigated the mechanics and design of composite materials with high stiffness and high damping in response to dynamic loads.