Accession Number:

ADA230147

Title:

Near-Field Acoustic Scattering from Rough Surfaces

Descriptive Note:

Corporate Author:

NAVAL OCEANOGRAPHIC AND ATMOSPHERIC RESEARCH LAB STENNIS SPACE CENTER MS

Report Date:

1990-01-01

Pagination or Media Count:

1.0

Abstract:

Criteria for the Fraunhofer approximation for scattering from a rough surface are reviewed and restated in a new convenient form. It shows the importance of recognizing that the scattering patch size increases with distance from a source of constant beamwidth. The importance of the common assumption of an incident plane wave is discussed. Very little practical sonar work satisfies the standard Fraunhofer criterion for the far field. Coherent and incoherent scattering is discussed and model simulation results for the Kirchoff approximation are presented. Results are consistent and show a strict application of the standard Fraunhofer criterion for the farnear field transition distance for scattering coefficient and those that show a relaxation of the criterion for incoherent scattered intensity. The two are reconciled by normalization applied to the scattered intensity to obtain the scattering coefficient. Significant differences do, however, remain for both the coherent and incoherent intensities.

Subject Categories:

  • Acoustic Detection and Detectors
  • Acoustics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE