### ASA 125th Meeting Ottawa 1993 May

## 2pPA9. Radiative transfer of ultrasound.

**Joseph A. Turner
**

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Richard L. Weaver
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*Dept. of Theor. and Appl. Mech., 104 S. Wright St., Univ. of Illinois,
Urbana, IL 61801
*

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*
Multiple scattering of ultrasound in an elastic medium containing discrete
random scatterers is modeled using radiative transfer theory. The uncorrelated
phases of the scattered field allow one to write an energy balance equation for
the spatially incoherent intensity. This ultrasonic radiative transfer equation
contains single-scattering and propagation parameters that are calculated using
the elastic wave equation. Polarization effects are included through the
introduction of an elastodynamic Stokes vector, which contains a longitudinal
Stokes parameter and four shear Stokes parameters similar to the four Stokes
parameters used in optical radiative transfer theory. The theory is applied to
a statistically homogeneous, isotropic elastic half-space containing randomly
distributed voids illuminated by a harmonic plane wave. Results on the angular
dependence of backscattered intensity are presented. It is anticipated that
this approach may be applicable to materials characterization through the study
of the time, space, ultrasonic frequency, and angular dependence of multiply
scattered ultrasound in elastic media with microstructure. [Work supported by
NSF Grant No. MSS-91-14360.]