Environmentally associated signal-to-interference variability in low-frequency active sonar

Abstract

An analysis has been conducted of the spatial and temporal variability of target echo-to-interference measurements made during Area Characterization Test I (ACT I) in 1992 on the West Florida Shelf in the Gulf of Mexico. The measurements were made for five bistatic geometries using explosive sources, a bottom-mounted horizontal receiving hydrophone array and an echo repeater ‘‘target’’ in 180 m depth water under downward refracting acoustic conditions. The bottom at the ACT I site was nearly flat of sand-silt-clay composition, and oceanographic and meteorological conditions were very quiescent during the test. In all respects these measurements could be described as having been in a quiet, well-behaved sonar environment. The observed temporal (standard deviation of 1.6 dB) and spatial (standard deviation of 2 dB) variability of the received signal-to-interference will be discussed in terms of physical causes and measurement error. [Work supported by ONR.]