Accession Number : AD0853975

Title :   Sound Propagation Study.

Descriptive Note : Annual summary rept.

Corporate Author : RAYTHEON CO NEW LONDON CT MARINE RESEARCH LAB

Report Date : NOV 1968

Pagination or Media Count : 93

Abstract : The Fast Field Program (FFP) is a numerical method, recently proposed by H. W. Marsh, of evaluating the exact solution of the hydrodynamical field equations. It is based on the Fast Fourier Transform (FFT) algorithm. Any case in which the exact solution can be expressed in the form of a Fourier type integral, including cases which embrace a layered inhomogeneous medium, yields an FFP solution. The FFP is especially useful in cases where the field is desired as a function of both range and depth. Formulations including two different exact solutions to the wave equation for a layered inhomogeneous medium and a single frequency, point source have been developed during the past year. The first does not require an evaluation of the discrete normal modes (if any exist) and the surface and bottom boundaries are included. Analytical solutions to the one dimensional reduced wave equation in terms of hypergeometric functions were used for examples for a Gulf of Maine profile. The second formulation allows a more general sound velocity profile, but requires the calculation of trapped modes when they exist. A general numerical integration method for solving the one dimensional reduced wave equation is used.

Descriptors :   *FOURIER ANALYSIS), (*HYDRODYNAMICS, SOUND TRANSMISSION), (*SOUND TRANSMISSION, UNDERWATER SOUND, INTEGRAL TRANSFORMS, NUMERICAL METHODS AND PROCEDURES, HYPERGEOMETRIC FUNCTIONS, WAVE FUNCTIONS, BOUNDARY VALUE PROBLEMS, PROPAGATION.

Subject Categories : Acoustics
      Fluid Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE