Apr. 29, 2009 When acoustic waves propagate through a given material, the ocean for instance, the sound waves respond to the properties of the fluid. Scientists can use these responses to probe the characteristics of the medium -- the ocean or the atmosphere, for instance -- and one particularly powerful way of doing this employs a technique called "time reversal." In time reversal, signals are played backwards to cancel out interfering noise.
The technique is used in astronomy to remove atmospheric blurring and in medical imaging to focus ultrasonic beams. It is also being developed for underwater communication in the ocean.
Now a group of scientists in Grenoble, France and Montevideo, Uruguay have developed a method based on time reversal that can reveal the characteristics of soft solids. In a pair of presentations, the team will report how they measure the elastic properties of soft solids by using surface or bulk acoustic waves. This allows them to characterize the tenderness of beef and monitor the ripening process of soft cheese.
Their approach is a promising low cost technique for future applications in food production and other industries. In medicine, for instance, measuring shear elasticity is a hot topic in neuromusclular disease, and it may be relevant to diseases in the brain or for monitoring changes in moving organs, such as the heart. Their method can also allow determination of the human skin elasticity.
The talk "Tissue shear elasticity assessment using time reversal" by Thomas Gallot et al and the talk "Time-reversal Rayleigh wave for soft solid characterization" by Javier Brum et al. will be presented at the 157th Acoustical Society of America Meeting to be held May 18-22 in Portland, Ore.
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