The general objectives of this investigation were to determine and study those characteristics of the sea floor that affect sound propagation and the prediction of sonar performance; to support underwater acoustics' experiments and theory by furnishing information on the mass physical properties of sediments and rocks in the form of geoacoustic models of the sea floor; and to develop models of the sea floor which include gradients of sound velocity and attenuation, density, and elastic properties. Specifically, the minor objectives were to revise and review earlier work on the relations between frequency and attenuation of compressional (sound) waves in marine sediments and on the relations between attenuation and sediment porosity. The major objectives were to determine and predict variations of the attenuation of sound waves with depth in the sea floor.

A study of marine sediments in three major environments of the North Pacific: the continental terrace (shelf and slope), abyssal plain (turbidite), and abyssal hill (pelagic). Laboratory values of the mass physical properties of the sediments (e.g., sound velocity, density, porosity, grain size, and others) are measured and computed and their empirical relationships and environmental differences are discussed.

In situ measurements were made of the velocity and attenuation of compressional waves and of velocities of Stoneley waves (from which shear-wave velocities were computed) at six stations in the sea floor off San Diego, California. Water depths ranged from 20 to 1130 meters, and sediment types ranged from medium sand to clayey silt. Sediment densities, porosities, and grain sizes were measured in samples taken at each station. The unique data obtained allowed tentative evaluations of models and equations, and computation of constants, for elastic and viscoelastic saturated, porous media. (Author).

A study of the acoustic and related properties of the sea floor in three major environments of the North Pacific: the continental terrace (shelf and slope), abyssal plain (turbidite), and abyssal hill (pelagic). Discussions cover the correction of laboratory to insitu values, and the prediction of in situ values. The methods developed are applicable to other areas and sediments.

Acoustic relaxation theory for visco-elastic media provides for sound propagation in unconsolidated marine sediments. For the frequency range of 14 to 200 kHz, dispersion for compressional-wave and shear-wave velocity is negligible for all practical purposes, but sound absorption shows significant changes. (Author).