HR: 14:40h
AN: S12C-03 INVITED     [PDF]
TI: Ultrasonic Waves in Strongly Scattering Media: a Symphony of Ultrasound That is Almost all Coda.
AU: * Page, J H
EM: jhpage@cc.umanitoba.ca
AF: University of Manitoba, Department of Physics and Astronomy, University of Manitoba, Winnipeg, MB R3T 2N2 Canada
AB: Waves traveling through strongly scattering materials can behave in unusual ways, and in this presentation, I will review recent progress in probing their behavior using ultrasonic techniques. In random systems, ultrasonic experiments on simple model materials (spherical beads suspended in a liquid, porous materials made from sintered glass beads) have shown how the coherent ballistic component can be separated from the dominant multiply scattered waves (the coda), allowing a rather complete picture of wave propagation in such systems to be established. These experiments have also helped to elucidate how multiply scattered waves diffuse, giving a unified physical picture of the relationship between the velocities of energy transport by diffusive and ballistic waves. These fundamental studies of wave transport by multiply scattered waves have facilitated the development of three new techniques in ultrasonic correlation spectroscopy (or coda wave interferometry) for measuring the dynamics of strongly scattering materials: Diffusing Acoustic Wave Spectroscopy (DAWS), Diffusing Reverberant Acoustic Wave Spectroscopy (DRAWS) and Dynamic Sound Scattering (DSS). Very different wave behavior can be observed by arranging the beads in an ordered crystalline array (a phononic crystal), giving rise to a complete bandgap through which the ultrasonic waves travel by tunneling. The presentation will end with a brief description of elastic wave diffusion in porous materials, where the multiply scattered ultrasonic energy is partitioned between P and S waves and remarkably strong scattering can be observed. Work performed with H.P. Schriemer, M.L. Cowan, Suxia Yang, J. Bobowskl, R. Holmes, J. Beck, J. de Rosny, D.A. Weitz, Ping Sheng and Zhengyou Liu.
UR: http://www.physics.umanitoba.ca/~jhpage
DE: 7200 SEISMOLOGY
SC: Seismology [S]
MN: 2003 Fall Meeting