Accession Number:

ADA276165

Title:

Ocean Acoustic Propagation Measurements and Wave Propagation in Random Media

Descriptive Note:

Corporate Author:

WASHINGTON UNIV SEATTLE APPLIED PHYSICS LAB

Report Date:

1993-04-01

Pagination or Media Count:

25.0

Abstract:

Over the last two decades, observations of acoustic scintillations in the ocean have been useful in testing theories that predict the statistics for WPRM. Ocean acoustic observations differ from scattering processes observed in other WPRM sub-fields in two important ways. First, the statistics of the refractive index can be determined accurately from oceanographic measurements. Hence, exacting tests of theories can be done when careful measurements of the medium and the wavefield are made synoptically. Second, the scattering of acoustic energy is predominantly influenced by the ocean internal wave field, which tends to exhibit statistical stationarity in many ocean regimes, and not by non-stationary turbulent processes, as observed in the atmosphere. We discuss spacetime acoustic propagation experiments carried out in three scattering regimes 1 weak, where the Rytov approximation is valid 2 moderate, where multiple scattering theory is required and 3 the case where multiple scattering in a single medium irregularity is encountered. A review is presented of the measurements and comparisons with theory. It is clear from field and numerical experiments that 2-point statistics cannot possibly explain the observations of intensity. Because two-point statistics are the norm when interpreting both medium and wavefield measurements, the possible failure of Gaussian statistics must be addressed. This has yet to be done. We will discuss remaining issues for which we believe further study is needed.

Subject Categories:

  • Physical and Dynamic Oceanography
  • Acoustics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE