Accession Number:

ADA048741

Title:

Frequency Spreading in Forward Surface Scattering.

Descriptive Note:

Technical rept.,

Corporate Author:

YALE UNIV NEW HAVEN CONN SYSTEMS AND INFORMATION SCIENCES

Personal Author(s):

Report Date:

1977-12-01

Pagination or Media Count:

42.0

Abstract:

An experimental study of frequency spreading in acoustic signals forward scattered from model tank wind driven water surfaces has been performed. The study employed wide band probing signals to doubly sample the surface scatter process. A high degree of precision and demonstrated repeatability was produced. Parameters varied in the study included grazing angle, surface roughness, wind direction, and acoustic wavelength. Rayleigh roughness parameters varying from 0.7 to 12. were studied. The results of the study consist of a large number of measured frequency spreading functions and an analysis of the frequency shift of the mean scattered power and RMS spread as a function of wavelength for each condition of wind and grazing angle. This analysis indicates qualitative agreement with current theory in the general form of the spread spectrum at high and low roughness, and in the linear dependence of the mean shift on frequency. The data showed a marked sideband asymmetry in symmetric geometric configurations, however, which is not consistent with any published analytical model. In addition, at short wavelengths, frequency spread seemed not to increase linearly with carrier frequency. Author

Subject Categories:

  • Acoustics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE