Accession Number : AD0863322

Title :   Reflectivity of Deep Sedimentary Bottoms.

Descriptive Note : Technical memo.,

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

Personal Author(s) : Lallement, B. ; Stangerup, P.

Report Date : 15 DEC 1964

Pagination or Media Count : 13

Abstract : A model for bottom-reflectivity loss has been developed in connection with bottom-reflection experiments made with explosive sources in the Mediterranean Sea. The bottom is considered as a fluid medium with attenuation losses. This model has been found to be a good approximation of variations of the reflection coefficient versus frequency and angle of incidence on the sea floor in the case of flat bottoms. Experimental results have been obtained for frequencies varying from 70 cps to 8 kc and angles of incidence from 20 to 85 deg. Examples of these results are given, including computation of critical angle, of ratios of densities and velocities in the different media, and of attenuation coefficient, and evidence of two sediment layers in a particular case. An attenuation law has been derived from the frequency dependence of the reflection coefficient. Pulse shapes of the first and the second bottom bounces have been related to theoretical phase shift. It is felt that this model is useful to predict bottom reflectivity and pulse distortion on smooth deep bottoms and will have to be improved for rough areas. (Author)

Descriptors :   (*UNDERWATER SOUND SIGNALS, OCEAN BOTTOM), REFLECTIVITY, ATTENUATION, MEDITERRANEAN SEA, MATHEMATICAL MODELS, SEA WATER, VELOCITY, DENSITY, SEDIMENTATION, ANGLE OF ARRIVAL, PENETRATION, PHASE SHIFT CIRCUITS, DEEP WATER.

Subject Categories : Acoustics

Distribution Statement : APPROVED FOR PUBLIC RELEASE