Accession Number : AD0466138

Title :   A DETAILED STUDY OF SOUND REFLECTIONS FROM A LAYERED OCEAN BOTTOM.

Descriptive Note : Technical rept.,

Corporate Author : SACLANT ASW RESEARCH CENTRE LA SPEZIA (ITALY)

Personal Author(s) : Stangerup, P.

Report Date : 15 MAY 1965

Pagination or Media Count : 44

Abstract : The effect of layered sediments on sound reflection from the ocean bottom has been investigated theoretically and experimentally. Very detailed, systematic and computer-aided calculations of the reflection coefficient of a twolayer bottom are made, using well-known theory and varying the following parameters: (1) velocity and density contrasts; (2) layer thickness normalized with respect to wavelength; (3) absorption in the sediments (in db/wavelength); (4) shear wave velocity in the lower layer. Calculations are made both for a harmonic source and for a broadband source analysed within certain bands around the harmonic source frequency. A series of curves is obtained representing the two-layer effect for a range of parameters that encompasses typical ocean bottom values. It is shown that absorption in the upper layer is of great importance in sound reflection, especially beyond a critical angle, but that moderate shear wave velocities have little effect. An octave band analysis of experimental data -- using a broadband source -- tends to support this theoretical two-layer model. (Author)

Descriptors :   (*OCEAN BOTTOM TOPOGRAPHY, SOUND TRANSMISSION), MODEL THEORY, SEDIMENTATION, ABSORPTION, VELOCITY, DENSITY, THICKNESS, HARMONIC ANALYSIS, BROADBAND, PROPAGATION, MEASUREMENT, REFLECTION, MARINE GEOPHYSICS.

Distribution Statement : APPROVED FOR PUBLIC RELEASE