Some Factors Affecting the Measurements of Bottom Reflectivity

Abstract

Bottom-reflection measurements were made in four different geographically smooth, nonsloping bottom areas. Reflection coefficients were computed as a function of angle from data obtained at two single frequencies, two frequency bands, and several pulse lengths. The experimental design and first area results are discussed elsewhere [J. Acoust. Soc. Am. 38, 707–714 (1965)]. Vertical hydrophone arrays were used in three of the areas and it was possible to make comparisons based on hydrophone separation. Average values of reflectivity for data taken at the same angle but for different bottom-reflection points within a small area are observed to differ by as much as a factor of two. Cores taken within the same reflection areas as the observed acoustic results also showed variations in sediment properties. Results obtained at the four locations are presented to show the degree to which it is possible to characterize a large geographic area from measurements taken over a very small area within it.