Studies of Observed and Predicted Values of Bottom Reflectivity as a Function of Incident Angle

Abstract

Using a deep source and deep receivers, measurements of the acoustic reflectivity of the ocean bottom at 1 kc/sec were made at an area in the Atlantic Ocean. The data, that is, the direct and the first-order bottom-reflected arrivals, were acquired digitally at sea and have been reduced via a computer program. The program computes the reflection coefficients based on peak pressure as well as the time-integral square of the pressure. The computer analysis also furnishes the travel time of each arrival, horizontal range, and incident angle for each transmission. The total number of data points considered exceeds 4000. Computations based on velocities, densities, and attenuations that have been obtained from an analysis of cores taken in the general area of the acoustic tests have been performed, using a theoretical model of the bottom. This model consists of many absorbing liquid plane parallel layers over one absorbing semiinfinite solid. Comparisons of the experimentally derived reflection coefficient as a function of incident angle are made with those obtained from the model, and the relevance of the complicated layering structure and attenuation of the bottom is discussed.