Single and multiple scattering in a random moving medium

Chapters 7 and 8 considered situations in which sound waves are scattered predominantly in their direction of propagation. Such scattering occurs when the sound wavelength λ is small compared to the outer scale of turbulence L , i.e., https://www.w3.org/1998/Math/MathML" display="inline"> λ ≪ L . The scattering can be described with the parabolic equation and its approximations based on geometrical acoustics and the Rytov method. The current chapter considers large-angle scattering with respect to the propagation direction, including backscattering. The large-angle scattering always exists in a random medium; however, it is relatively small if https://www.w3.org/1998/Math/MathML" display="inline"> λ ≪ L . On the other hand, if https://www.w3.org/1998/Math/MathML" display="inline"> λ ≳ L , the large-angle scattering becomes comparable to that in the propagation direction.