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				ID			419
				Category			Acoustic
				Project Date			5/4/2007
							Acoustic Spatial Self-Focusing through a Random Medium using Iterative Time Reversal
				Title
				Description			Time symmetry in the acoustic wave equation can be exploited to produce pressure field focusing on a reflective object. An acoustic time reversal mirror (TRM) consisting of four elements was constructed to observe pressure focusing through a random scattering array. Varying the reflectivity ratio of two targets opposite the TRM allowed us to investigate its focusing capability defined by the relative pressure maxima as a function of spatial coordinates. For slightly different reflectivities, the ratio of the pressure maxima measured by the reflectors was found to decay geometrically with each successive time reversal iteration agreeing with the theory presented by Prada, et al. Asymptotic limits were observed in the maximum amplitude ratio for all reflectivity ratios investigated. These limits prevented the observation of geometric focusing for large reflectivity ratios. Some spatial limitations to focusing are discussed.
				Author(s)			Donarski, Matt
							Fuller, Franklin
				Equipment Built
	V: SRepJul99b Updated:  7/8/99
				MXP Report ID			0770
				Report Location			File Cabinet
				AIP Classification
				Project URL			http://mxp.physics.umn.edu/s07/Projects/S07_TimeReversedAcoustic/